I'm aware there are different kinds of conservatives and that libertarians claim to focus more on individual liberty than the others do. The question is whether either conservatives or libertarians have a coherent understanding of what liberty entails.
Members of the government can break the law, but the government writes the laws, so if taxation is legal, it's not theft.
You may say it's theft in a deeper, moral sense, if not in a strictly legal one. But then we're at the level of the social contract, as I discuss it in the article. What are our foundational, pre-legal obligations to each other in forming a social refuge from the wilderness? Don't we have to compromise on our absolute liberties?
Libertarians want to have it both ways, both maximal individual liberties plus the benefits of society--unless they move to a place like Alaska that allows people to live more on their own without all of the latter benefits.
I don't know that libertarians are especially altruistic and eager to give to charity. On the contrary, they seem self-obsessed to me, going on and on about what they deserve as individuals and not so much about what they owe to others, including taxes to pay for the social benefits that all members enjoy (the benefits of being in a society as opposed to being alone in the wilderness).
If they do give to charity, they might be doing so out of guilt, since they'd be giving with one hand what they take from the other. By voting for Republicans or for the free-market Libertarian party, they're helping to turn American society into a tribal wasteland and to rig the market for the plutocrats, by stripping the government of its regulatory powers. So they're a large part of the problem that charity's needed to fix.
You seem to think the "render unto Caesar" line means Jesus thought religion should be separated from affairs of state, so that his followers should lead a double life, pretending to revere the emperor while secretly worshipping God.
But it's ludicrous to think there's a whole philosophy there about church-state separation that would justify anything like the hypocrisy of American conservative "Christians." Jesus was just avoiding a trap that his questioners were laying for him, by the equivalent of putting forward a pun, taking advantage of the fact that the coin had the name and face of Caesar on it. To keep the coin would be "theft," as if the emperor owned everything in his realm.
Thus, Jesus was ducking the deeper issue (of whether God is really present everywhere in the world, including in economic transactions), by focusing on superficial details of the situation.
Jesus's morals were still absolute, but he cared more about the state of mind than superficial habits, more about the spirit than the letter of the law. If paying taxes or being a good citizen in the secular sense means failing in your spiritual obligations to God, Jesus would obviously have disapproved. And that's clearly what American conservative Christians have done, including the Trump supporters, the warmongers, the social Darwinians, the plutocrats, and so on.