I don't know if I should be mentioning this, because I don't really want to defend them or thier practices, but I am aware of a group called "We the People" who exist to challenge the US government on certain constitutional issues, one of them being the consitutionality of the income tax as it is currently enforced.
They hold as you do that income as defined in the consitution is a very limited form of income and that the Supream Court ruled that the 16th amendment gave the gov no new powers, etc, etc...
They also have issues with the Wars Power Act(sp?)
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