I haven't read the entire thread, so maybe it's been already asked. If it's the case, I apologize.
Mohammed was a human, and the difference between Mohammed and Allah is crystal clear in Islam.
Yet, even though he is human, he is apparently supposed to have no character flaws (at least, Muslims tend to be very defensive when someone points them out).
Does it mean that Mohammed had only done good works during his life, and not a single bad one?
Does it mean that he is better than any human? Or can an ordinary human reach his level of perfection?
Finally, are there Muslim sects who distance themselves from this belief, ie that Mohammed was perfect?
I won't hide that, to me (atheist), the unquestioning respect of Mohammed, a human being, sounds a lot like idolatry. I'm one who believes that no human can possibly be perfect, so putting him on such a pedestal sounds like making him into a deity of sorts.
Edit: I realize my tone may sound harsh. I certainly don't intend to be, as I really appreciate your efforts in this thread, as well as your honesty
The idea that Prophet Muhammad (s) was perfect is a Shia belief only. Unfortunately, some Sunnis have been affected by the Shia propaganda on this topic, but the true position of the Sunnis is that nobody but Allah is perfect. I wrote this article for another forum, and I shall post it here:
No Prophet is Perfect
Muslims believe that only the Creator Allah Almighty is perfect. On the other hand, creation cannot possibly be perfect as this is an attribute only Allah Almighty can posses. Humans, who were created simply out of dust, are an excellent example of imperfection. All humans commit mistakes and sin.
As Perfection is an attribute of Allah, Imperfection then is an attribute of human beings. This is why the imperfect human beings bow down to the perfect Creator. Indeed, to ascribe an attribute of Allah to a human being is an act of Shirk; it is ascribing partners to Allah Almighty. If we believed that a human being was perfect/omniscient/omnipotent, then we are guilty of Major Shirk (associating partners with Allah, or indirect polytheism).
From the very beginning of time, Prophets have taught humanity this same message. Unfortunately, people have always been led astray by Shaytan who tricks them into commiting Shirk. The prime example of this are the Christians, who eventually started giving Allah’s Attributes to Prophet Jesus (عليه السلام

. Prophet Jesus (عليه السلام

himself would preach
Tawheed (oneness of God), and yet his astray “followers” started attributing Prophet Jesus (عليه السلام

to God! The Quran clearly says what the fate of such people will be: on the Day of Judgement, Prophet Jesus (عليه السلام

himself will testify against these so-called “followers.”
It should be noted that the story of Prophet Jesus (عليه السلام

is mentioned in the Quran not only for the Christians but in fact more for the Muslims. After all, a Christian would reject the Quran, so the primary audience of the Quran is the Muslims. The example of the Christians was put forth in the Quran as a reminder to Muslims so that Muslims don’t fall into the same trap.
Only Allah Almighty is the One incapable of forgetting or making a mistake. All human beings can make mistakes. This is the definition of being a human being.
The Quran
We will now proceed to prove without a shadow of doubt that Prophets are not infallible according to the Quran. We will show how the Quran refutes all three points and how Prophets can sin, do make mistakes, and do forget.
The most obvious example is that of Prophet Adam (عليه السلام

. We cannot fathom how the Shia factor in the story of Adam (عليه السلام

. Allah Almighty forbade Prophet Adam (عليه السلام

from going near a tree in Paradise. But Shaytan convinced Prophet Adam (عليه السلام

to sin and violate the Law of Allah.
In Verse 20: 121-122 in the Quran, Allah Almighty says:
Thus did Adam disobey his Lord, so he went astray.
Then his Lord chose him, and turned to him with forgiveness, and gave him guidance. (Quran, 20:121-122)
Prophet Musa (عليه السلام

also committed a mistake of killing an Egyptian man. In Verse 28:16 of the Quran, Allah Almighty says:
He [Musa] said: ‘My Lord! Verily, I have wronged myself, so forgive me.’ Then He [Allah] forgave him. Verily, He is the Oft-Forgiving, the Most Merciful. (Quran, 28:16)
Prophet Dawood (عليه السلام

commited the sin of passing judgement before hearing the case of the second disputant. In Verse 38:23-24 of the Quran, Allah Almighty says:
…and he [Dawood] sought forgiveness of his Lord, and he fell down prostrate and turned (to Allah) in repentance.
So We forgave him that, and verily, for him is a near access to Us, and a good place of (final) return (Quran, 8:23-24)
And our Prophet Muhammad (صلّى الله عليه وآله وسلّم

was rebuked by his Lord for several things that are mentioned in the Quran, such as the following in verse 66:1:
O Prophet! Why do you forbid (for yourself) that which Allah has allowed to you, seeking to please your wives? And Allaah is Oft-Forgiving, Most Merciful. (Quran, 66:1)
In another verse in the Quran, the Prophet (صلّى الله عليه وآله وسلّم

is rebuked for not listening to an old man:
(The Prophet) frowned and turned away, because the blind man came to him. But didn’t you know that perhaps he might grow (in spiritual understanding)? Or that he might have received an important lesson, and the teaching might have profited him. As to the one who thought he was self-sufficient, you attended to him - though it was not your fault that he did not grow (in spiritual understanding). But as to the one who came to you earnestly seeking and with reverence, of him you were unmindful. It should not be so! (Quran, 80:1-11)
In another instance, the Prophet (صلّى الله عليه وآله وسلّم

decided to free prisoners in the Battle of Badr, but Allah wanted him to first seek justice by punishing the enemies of Islam. And so it was that Allah corrected the Prophet (صلّى الله عليه وآله وسلّم

in the Quran and demanded that the war criminals be brought to justice. This is narrated in Verse 8:67.
There should be no doubt left in the minds of anyone that the Prophets cannot only make mistakes but they can also commit minor sins. No human being is above this, and to believe such a thing is to commit Shirk. The Prophet (صلّى الله عليه وآله وسلّم

will reject those who dare elevate his status to that which is not befitting of a man.
The Prophet (صلّى الله عليه وآله وسلّم

repeatedly told his followers that he is just a man and no more. Indeed, the Prophet’s modesty is a shining example to us all. The Shia have commited a grave sin by associating the Attributes of Allah to human beings.
The Prophets were the best of the human beings. There is no doubt about this. We should respect all the Prophets and they are leaders to humanity. But we should not exalt them to the status of God, or else we will be falling in to the same trap as the Christians fell into.
Allah Almighty says in the Quran:
“O People of the Scripture, do not exceed limits in your religion beyond the truth and do not follow the inclinations of a people who had gone astray before and misled many and have strayed from the soundness of the way.” (Quran, 5:77)
Shaikh Ibn Tamiyyah
Shaikh Ibn Tamiyyah said in Majmoo’ al-Fataawa:
"The view that the Prophets were protected from major sins (kabaa’ir) but not from minor sins (saghaa’ir) is the view of the majority of the scholars of Islam… It is also the view of the majority of the scholars of tafseer and hadeeth, and of the fuqahaa’. Nothing was reported from any of the Salaf, Imams, Sahabah, Tabi’een or the successive generation that does not agree with this view.
"What has been narrated from the majority of scholars is that they (the Prophets) are not infallible with regard to minor sins, but they are not left to persist therein. They do not say that this does not happen under any circumstances. The first group from whom it was narrated that they are infallible in all cases, and who say that the most, are the Raafidis (Shi’ah), who say that they are infallible and protected even against forgetfulness and misunderstanding…"
Prophets as Role Models
A typical Shia response to the idea that Prophets can commit minor sins is the following:
Allah has commanded us to follow the Messengers and take them as our example. The command to follow them is taken as meaning that everything they did is an example for us to follow, and that every action and belief of theirs is an act of worship. If we suggest that that the Messenger committed a sin, there will be a dilemma, because that implies that we are commanded to imitate this sin which was committed by the Prophet because we are commanded to follow his example, but at the same time we should no agree with it or do it, because it is a sin.
This argument would only be valid and appropriate if the sin is hidden and not obvious in such a way that it could be confused with acts of obedience. But Allah has explained to His Messengers where they went wrong and enabled them to repent without delay. Thus, there is no confusion on the matter, and the Muslims know what is right and what is wrong. Shaikh Muhammed Al-Munajjid responded to this Shia argument by saying:
"This argument is valid and is appropriate if the sin is hidden and not obvious in such a way that it could be confused with acts of obedience. But Allah has explained to His Messengers where they went wrong and enabled them to repent without delay."
In fact, the believers can imitate the Prophets in the manner in which they repent and seek Allah’s Help. For example, the example of Prophet Adam (عليه السلام

touching the forbidden tree serves as a good reminder for all Muslims; we know from this story that we should obey Allah and that when we disobey Him, then we should repent immediately and sincerely like Adam (عليه السلام

did.
Although the Prophets are not infallible in totality, they are infallible in the specific aspect of conveying the Message of Islam. For example, the Prophet (صلّى الله عليه وآله وسلّم

would never make a mistake when he was reciting the Quran. Angel Jibrael (عليه السلام

instructed the Prophet (صلّى الله عليه وآله وسلّم

to “read” to which the Prophet (صلّى الله عليه وآله وسلّم

responded that he could not read. But Allah allowed him to read and recite when it came to the Quran because it was Allah Himself who would ensure that the Prophet (صلّى الله عليه وآله وسلّم

would convey it correctly. The Prophet (صلّى الله عليه وآله وسلّم

was at first worried that he would forget the words of Allah, but Allah reassured Him that Allah has taken the responsibility of ensuring that the Prophet (صلّى الله عليه وآله وسلّم

conveys it with 100% accuracy.
Allah says in the Quran:
“Your companion (Muhammad) has neither gone astray nor has erred. Nor does he speak of (his own) desire. It is only a Revelation revealed. He has been taught (this Quran) by one mighty in power.” (Quran, 53:1-5)
The Ummah is agreed that the Messengers do not make mistakes when it comes to conveying the message. They did not forget anything that Allah revealed to them, except for things that were abrogated. And Allah guaranteed His Messenger that he would remember it and would not forget it, except for that which Allah wanted him to forget, and He guaranteed to remember the whole Quran in his heart. Allah declared:
“We shall make you to recite (the Quran), so you (O Muhammad) shall not forget (it).” (Quran, 87:7)
So the fact that the Prophet (صلّى الله عليه وآله وسلّم

is not infallible in totality does not mean that the Message will be compromised at all. The reason for this is clearly stated in the Quran, namely that Allah has taken the responsibility:
“It is for Us to collect it and to give you (O Muhammad) the ability to recite it (the Quran).” (Quran, 75:17)
Hence, the Prophet (صلّى الله عليه وآله وسلّم

could not make mistakes when it came to religion namely because Allah ensured this. On the other hand, it is not impossible for the Prophet (صلّى الله عليه وآله وسلّم

to make minor mistakes on issues that have no bearing on his delivering the message. For example, he could make minor mistakes when it came to non-religious issues, such as agriculture, carpentry, and other such secular matters. Making minor mistakes in such matters does not put into question the Prophet’s ability to convey the Message.
Shaikh Muhammed Al-Munajjid declared:
"With regard to worldly matters…with regard to agriculture, medicine, carpentry, etc., he was like all other people. Allah did not tell us that he was sent to us as a businessman or a farmer or a carpenter or a doctor. His mistakes in these fields are quite natural and do not impact on his Message at all."
In one of the Prophetic Sayings, we read:
The Prophet (صلّى الله عليه وآله وسلّم
came to Madinah, and they were pollinating the date-palms. He said, “What are you doing?” They said, “We always used to pollinate them.” He said, “Perhaps if you do not do that, it will be better.” So they did not do it, and the harvest was lacking. They mentioned that to him, and he said, “I am only a human being like you. If I tell you to do something with regard to religion, then follow it, but if I tell you to do something based on my own opinion, I am only a human being.” (narrated by Muslim, 2361).
We note that the Messenger (صلّى الله عليه وآله وسلّم

made a mistake in this worldly matter, because he was like all other human beings. But this does not take away from his greatness as a Prophet. A Prophet is not expected to know extraneous things such as how to fix an automobile radiator, solve quadratic equations, or other such matters which do not pertain to his Prophethood nor do they aid him in his mission to spread the religion of Islam to the corners of the globe.
The Standing Committee
The Standing Committee, one of the most respected scholarly bodies of Islam, was asked:
Do the Prophets and Messengers make mistakes?
The Standing Committee replied:
"Yes, they make mistakes but Allah does not let them persist in their mistakes, rather he points out their mistakes to them as a mercy to them and their nations, and He forgives them for their mistakes, and accepts their repentance by His Grace and Mercy, for Allah is Oft-Forgiving, Most Merciful, as will be clear to anyone who studies the verses of the Quran which speak of that."
(Source: Fataawa al-Lajnah al-Daa’imah, 3/194)
Greatness of the Prophets
There is absolutely no doubt that the Prophets are the best of human beings. It does not take away from their character at all to say that they are not perfect, or to say that they can commit minor mistakes and such. In fact, this only increases them in their greatness. First off, the Prophets do not commit major sins, but only minor ones. And Allah allows them to commit these sins so that He increases them in their faith when they ask for repentance. When a person sins, and then repents, Allah increases him in status for this.
Yes, sins are a shortcoming, but only if they are not accompanied by repentance, for repentance brings forgiveness of sin, and does not contradict goodness or bring blame upon a person. Rather, in many cases a person may be better after repenting than he was before he fell into sin. It is well known that no Prophet committed sin except that he hastened to repent and seek forgiveness. The Prophets did not persist in sin or delay repentance, for Allah protected them from that, and after repenting they became better people than they were before.
Conclusion
The debate over the issue of the Prophets’ infallibility is completely unnecessary, since the Quran itself mentions several instances in which Allah is reprimanding the Prophets for making a mistake. We have cited some of these verses in this article. These verses should be enough to convince the unbiased viewer that the Shia idea that their Imams are infallible is an exaggeration and blasphemous innovation that runs contrary to the Quran.
Simple logic dictates that it makes little sense for the Prophets to be asking for forgiveness from Allah unless they were capable of comitting mistakes and minor sins in the first place; otherwise, why would there even be a need to ask for forgiveness? If a person does not commit sins, then there is no need to ask for forgiveness, and yet we find that the Prophets repeatedly asked for forgiveness. This can only mean that they did commit mistakes and minor sins, although they hastened for repentance.