I am sorry that you have rejected Christianity, and I would like to clear up a couple of things.
Biblical Christianity is authoritarian in the sense that God has established various authority structures and cares deeply whether His people respect what He’s established. It is not authoritarian in the sense that it requires an authoritarian political system. There is nothing about Christianity that would keep a believer from enjoying living in a “world of individual liberty.” Christians can flourish under freedom just as much as can non-Christians.
Also, let me respectfully suggest that you’re missing the point in I Samuel 8. The people did not “convince” God to do “something He didn’t want.” First, you’ll notice that verse 6 says it was displeasing in SAMUEL’S sight — not God’s. Second, God isn’t “convinced” to give them a king — He turns them over to their own foolishness to allow them to discover that they would be much better off if they did not reject God and the blessings He has in store for them. Third, in the rest of the chapter, God is warning them of the consequences of their wrong desires — which He knows because He is omniscient, etc.
If you’re concerned about liberty, you should be happy with this incident. God allows them to experience the disastrous results of their choice to reject Him.
I would be interested in other places in which you believe the Bible is contradictory — because I do not believe it is contradictory in any way.
I am also intrigued by your denial of the authoritativeness of the Bible. Do you know of any other authority which accurately predicted hundreds of events in great detail hundreds of years in advance? Also, I suspect you find science to be an impeccable authority — despite the scientific errors which are discovered nearly every day. Have you yet figured out what you should/should not eat in order to avoid cancer? I can’t keep up with the conflicting “facts.”
Finally, I agree with you that Christians frequently act inconsistently with the teachings of their faith — but I see that as a bad thing — tragic, really.
As a political libertarian (and a non-Christian) if I wanted to argue the case for political libertarianism to a biblical orthodox Christian I would not argue the Bible endorses or is the source of the concept of political liberty as found in the Declaration of Independence (it does/is not). Rather I would argue the Bible is compatible with the idea of political liberty. And it makes good sense for orthodox Christians to endorse the concept. If, in the grand scheme of things, it's most important for Christians to "save souls" by missionary or conversion efforts (as opposed to fighting a "culture war") then it makes sense that an evangelical Christian chiefly be concerned that he has his political/religious liberty to proselytize effectively and in fact save souls.
In a closed, controlled society where just about everyone believed in the same kind of orthodox theology, it makes sense, from an orthodox Christian perspective, to forbid heresy, if it were just a matter of setting mousetraps to keep the house free of mice, as it were. Samuel Rutherford, though he may have been mistaken about Romans 13 on strict biblical grounds, rejected religious liberty on grounds entirely compatible with the Bible:
“It was justice, not cruelty, yea mercy to the Church of God, to take away the life of Servetus, who used such spirituall and diabolick cruelty to many thousand soules, whom he did pervert, and by his Booke, does yet lead into perdition.”
– Samuel Rutherfurd, “A Free Disputation Against Pretended Liberty of Conscience.” (1649).
However, the experience of religious disagreements within Christendom made such a political-religious consensus nigh well impossible. In short, if you give the civil magistrate the power to forbid religious heresy or enforce orthodoxy, chances are, you'll end up on the receiving end as a "heretic." Not only do Roman Catholics and evangelical/reformed Protestants irreconcilably differ on religious truths, but within Protestantism, the sects differ in meaningful ways. Even among the "sola scriptura" orthodox Trinitarian understanding of Protestantism, sects differ in such serious ways that if we didn't recognize religious/political liberty, dominant sects would use the power of the state to persecute dissident sects. Indeed, the rationale that I have just laid out is the story of how religious/political liberty came to Christendom. It wasn't a matter of "finding" these concepts in the Bible or the longstanding traditional understanding thereof, but rather through experience of warring and blood shedding among sects that concepts of religious and political liberty emerged and gained hold in Western Society as a way to "keep the peace," as it were.