What is Caesar's?
Taxation is STILL Theft
If one were to give unto Caesar what is Caesar's, then Caesar would starve. For nothing that Caesar has confiscated truly belongs to Caesar. It belongs to the one who has earned it. A thief does not rightfully own that which he has taken by force. The victim has a right to full compensation for his losses or damages. And the aggressor must pay interest. To force someone to pay for services that he doesn't want is no different - no matter who takes the role of the transgressing party.
Even if it were possible for the money to be used wisely or for good - which is rare in politics - the ends never justify the means. Even social anarchists who claim that property and the marketplace are evil, can only enforce their communist utopia on the masses through an authoritarian state which redistributes wealth and dictates the economy. This is precisely what happened with the creation of the Soviet Union.
The "invisible hand," as Adam Smith called it, is the real regulator. Caesar can only pretend. Laws written on paper are only laws written on paper. To the extent that they are enforced through a militaristic police force, they create black markets of violence and corruption. The greater the militarization, the greater the violence and corruption. In the real world, contracts between sovereign individuals govern society. In the real world, competition destroys corruption. In the real world, monopolies cannot grow as big as Caesar.
Were the organized church to embrace this simple fact, It would benefit immensely. Many of the functions currently carried out by the confiscatory state could be (and have been) carried out successfully (and completely voluntarily) by the church. Some churches have insurance agencies such as Thrivent Financial which serve their own communities. Church-sponsored insurance can easily expand into all realms traditionally commandeered by Caesar.
Were Catholics, Baptists, and several other major denominations to simultaneously proclaim the self-evident immorality of taxation, the evil state could be abolished overnight in all of Christendom.