It occurs to me that many of our States’ income tax codes violate our Constitution. Here’s the relevant clause, from the 14th Amendment’s Article I:
No State shall…deny to any person within its jurisdiction the equal protection of the laws.
Any income tax law that taxes citizens differentially plainly does not afford all citizens equal protection of the (tax) law. Such laws confiscate the incomes of some people far more than it does others, and such laws that exempt some people from paying the tax favors those folks over others who must pay.
States’ income tax laws that do not tax every one equally must be found unconstitutional. That such a ruling would disrupt State budgets is no reason to continue this violation.
That principle applies, or should apply even if not strictly constitutionally, to our Federal income tax code, also. In particular, the 16th Amendment authorizes a Federal income tax, but it in no way authorizes the Federal government to tax Americans differentially from each other.