“They do have different rates when they earn money in different brackets, but the rules are the same for everyone”
Huh? If one person is taxed at one rate and another another, obviously the rules are not the same. I might as well say that if black people’s income is taxed at ten percent and white people’s at fifteen the same rules apply, because it is ten for blacks and fifteen for whites whether you’re black or white. That’s nonsensical.
“SCOTUS has ruled in the past that graduated tax rates are fine”
Bad form. I couldn’t win the argument that racial segregation in public schools violates the 2nd amendment by saying SCOTUS struck it down with Brown. You know that whatever SCOTUS ruled they didn’t argue like you that progressive rates aren’t unequal. They’d say there is legitimate state interest in discriminating. Or they’d do what they usually do and say it fails the “strict scrutiny” standard, whereby it only strikes down laws that affect minority groups, voting rights, and their preferred sections of the Bill of Rights.
Needless to say just because SCOTUS doesn’t recognize economic classifications as worthy of 14th amendment smackdowns doesn’t mean they aren’t (psst, they’re wrong a lot).
Appropos of SCOTUS, I suggest you read Harper v Virginia Board of Elections. The reasoning isn’t applied to the income tax no doubt because of the courts’ irrational “strict scrutiny” standard for laws affalecting voting (among other things) and “rational basis” for taxation. But it is enlightening. It says voting qualifications based on wealth violate equal protection.
Ever since, and before, “poll tax” has been a dirty word, implying racism, and restricted to meaning something to do with voting. But of course there are all sorts of poll taxes, the income tax being one. The only reason SCOTUS knocked down economic discrimination in voting status but not income status is, again, because of the misguidedlu bifurcates scrutiny system. The same logic applies.