I'm not disagreeing that the income tax was initially sold as a small and limited tax, but I don't see why that's relevant. Subsequent congresses--elected by the people, with every seat in the house coming up every 2 years--expanded the tax with changes signed into law by the president, also elected by the people. The people accepted this. Further, the text of the amendment didn't place any limitations on who would be taxed or how much. If we didn't want the tax to expand, we could have limited it, through our representatives, through our president, through our state legislatures.
My second point still stands: if we don't like it we retain absolute control over ending it. Our failure to exercise our power is our own failure, and that's why the income tax cannot possibly be called theft.