For some definition of "legitimate"... it would still be nice if some progressive expert could articulate particular reasons why regressive taxes are good if they have particular qualities, rather than just saying "we like this tax, but not other ones that seem similar to it". I'm not seeing hypocrisy, but rather a line of thought that hasn't been pursued all the way to its natural conclusion. If someone were inspired to make that pursuit, we could come to a better understanding. Although I am sympathetic to progressives, most would say I am unqualified to undertake that pursuit myself.