The only reason the 16th amendment exists is because of a SCOTUS decision. Article I, Section 8 says: The Congress shall have Power to lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts and provide for the common Defence and general Welfare of the United States; but all Duties, Imposts and Excises shall be uniform throughout the United States. Furthermore Article I, Section 3 says: Representatives and direct taxes shall be apportioned among the several States which may be included within this Union, according to their respective Numbers.
Literally built into the US Constitution is the right of the government (both Federal and State) to tax. They are free to tax you 110% of what you actually earn, should they wish. It's legally impossible to call it theft. There's nothing "radical" about this view - what's radical is all of the unamerican asshats who go around blabbering about how great MURCIA is, until they're asked to pay something and then it's "MURICA DUN TERK OUR MONIES". I'm just tired of the stupidity.