Considering that other nations with similar growth rates have much higher taxes, I'd say the evidence is that our current tax rates amount to a giveaway for the rich. Of course, they also happen to be the ones with real political power (see Grover Norquist), so nothing is likely to change any time soon.
Considering that other nations with similar growth rates have implemented VAT, I'd say the evidence is current American tax rates don't amount to a giveaway to the rich. Rather the opposite in fact.
I'll point out what I believe the other commenter was alluding to.
1.Consumption taxes are generally considered regressive because poorer people end up consuming a greater proportion of their incomes and thus paying taxes again on more of their earnings.
2.People who talk about a 'giveaway to the rich' or who advocate for 'tax the rich' generally mean to draw a distinction and say that the rich need to pay an even higher proportion of taxes than the do at the moment. 'The rich' is seldom (I believe never) meant as metonymy.
3. Advocating for consumption taxes is thus advocating against taxing the rich more, and vice versa.
