I didn't claim that you CAN'T be a liberal Christian, or a theocrat Christian, or anything else. What I said is that Jesus did not specifically advocate for those ideologies.
I would make the argument that Jesus himself had very little to say about politics.
You are wrong.
Dissonance in Duty to One's Self Versus Duty to Others
The principles of Libertarianism are self-reliance and the freedom to succeed on a personal level by your own merits and hard work. Those values are not inconsistent with Christ's teachings. Indeed, the Parable of the Talents can reasonably interpreted to suggest that Christ calls upon His followers to reach for personal excellence and not to squander their gifts.
However, the instruction for personal excellence is obviously less important that His instructions to care for other people. Christ says time and time again, in parable and in sermon, and demonstrates through His actions that He expects His followers to care for each other. Indeed, not just for each other, but for all Man. He tells us to go and clothe the naked, feed the hungry, etc. He tells us that what we do to the least of our fellows we visit upon Him, and reinforces that relationship by calling upon us to love each other has He has loved us.
And just as He cared more for us than His own corporal interests so too does he call upon us to place others' needs ahead of our own when He tells us to give ours coats to those who sue us.
How to Best to Execute Care for Others
The takeaway is that care to others is a higher duty to which more is owed than pursuing excellence. As such, we must examine what the best way is to provide care to others. I'm going to use standard of living as quick and dirty measure for care for others. Populations with higher standards of living live longer, happier lives, and generally have more access to the Word than those with lower standards of living. Given the application of standard of living as a measure for care for others, liberal democracy seems to be a pretty good way to ensure care for others, generally.* People living under liberal democracies generally have higher standards of living than those under other forms of government, and consequently provide superior care to others. I think that the value of a liberal democracy is something we can generally agree upon.
The question then turns to what style of governance best suits the values of Christ, in this case Liberal or Libertarian styles of government. The Libertarian government values individual hard work and individual determinism highest. In contrast, the Liberal government values protection of the general welfare. Protection of the general welfare broadly includes ensuring that the least capable of those in society have food, shelter, and the necessities of life. Now neither of these virtues are in conflict, by themselves, with His message, but the Liberal value holds to the higher duty of care to others and subordinates the responsibility of the individual to himself. This value determination is in line with the message of Christ that individual excellency is important, but not as much as caring for your fellow man.
The General Versus the Specific
One may argue that Christ's message was one of personal responsibility and therefore the collective, in itself, does not have a responsibility to execute care for others. I reject this. Assuredly, His message is a call to personal action, but it is also a call to communal action. This is demonstrated by the fact that He came for all the nations of the world and regularly gave His directions to us as a flock, rather than as individuals. As such, we are called to work together utilizing social institutions to execute our duty to care for others. This is tacitly understood by most churches that provide charity on behalf of the congregation, rather than in the name of individual members.
Having established a communal duty to care for others, consider that government is the highest and most far reaching social institution in existence. As such, it makes sense to utilize the government as a means to provide care to others. Doing so makes use of economies of scale and other benefits that large institutions have over smaller groups. Consequently it is just and right for governments to provide care for others as doing so furthers His instructions to us. In order to do so, a government obviously needs revenue coming from taxes. As demonstrated by His statements that those who have much should extend their wealth to those with less, it is appropriate that we tax from the haves to give to the have-nots.
*(Note that I mean "liberal democracy" in the technical sense, not on a conservative-liberal, right-left scale.)