I can’t go to your house and simply demand your money — you don’t have to give it to me. If I use force, you can defend yourself. But for some reason we have accepted the idea that I can go to your house with several armed men and force you to pay up, as long as I have a warrant from the IRS.
Taxation is a criminal activity, and legalizing it puts the government in the business of running a criminal institution. If we can’t morally approve of an individual committing theft, we certainly shouldn’t approve of very many people doing exactly the same thing.