In effort to reply to main points I have to try to summarize them. I am attempting to do so accurately and not misrepresent you. Any mistakes made are honest ones.
Point one-Biden vilified his opponents when the chips were down after Iowa and it worked, so trying to immunize him against a similar strategy is unfair.
From the article linked the example of "sharpened attacks" on Buttigieg consisted of pointing out that at present his experience consists of being mayor in a moderate sized city. As you touched on, that can be called true, because it just flatly is. It is also not "vilification" in any sense of the word. I'd actually expect that Buttigieg would take it as encouragement to build his resume and try again.
I also don't see where Biden used any "red scare" attacks on Sanders. He was quoted talking about electability and how the GOP would use Sanders self identification as a socialist against not only Sanders but every Democrat down the ballot in November. Again, this can be called true because it just flatly is. Saying "if you hand them a club they will hit you with it" isn't vilifying. It isn't really even saying that the club is in itself a bad thing. It is just acknowledging the existence of the club and the reality that the opposition will use it if they have the chance.
Point two- the US electorate needs to get over the cold war and embrace the reality of socialism.
Probably so, but acknowledging the need does not justify a pretense that it has happened. The socialism "scare word" has and still does work in USian politics. It isn't "red scare" because clearly we have collectively relegated Russia into 'vanquished enemy' status and don't really worry all that much about 'a member of the US communist party is just a spy for the USSR.' What it is though is a widespread identification of socialist economic theory as 'failed.' Correctly or incorrectly, USians in the electorate predominantly attach 'socialism' as 'communism' as USSR and credit that economic theory as how the USSR lost the cold war. They are also constantly grasping onto every anecdote of a European country nationalizing anything and experiencing a bad consequence, and every anecdote where such nationalization "had to be given up as a failure." The only solution I see here is widespread education in economics applied over generations, not any sort of "embrace the self declared socialist and see if he can make a magical turnaround happen."
Point three- the pending revolt of disappointed youth.
It may very well seem like this is "right around the corner" and that these youth and their movement are so singularly put out and their issues so singularly critical that action to appease them has to be taken immediately before the whole place goes up in flames. I absolutely agreed with every word of that idea, and every argument presented in support of that idea. I hunkered down ready to eagerly support the pending revolution when it inevitably happened as a result of the pending irrefutable evidence that the electoral system was totally broken.
But somehow 1973 came and went and there was no youth revolution to be found. The person I heard those arguments from dropped out of the electorate in disgust, but showed less enthusiasm for an actual bloody revolution than I had. He reentered the electorate in the 90s as a Republican.
Conclusion...the guy on the street corner with the sandwich boards saying "the end is near" might be right. When the end does come there will undoubtedly have been one of those guys and we need to credit him for it. But there definitely will be one of those guys at the time because there always is, and all the rest of them will still have been wrong.