WC, just because someone pays less than 13.7% in taxes doesn't mean they're a hypocrite if they think that millionaires should pay more. I don't think those making less than $50K per year should have high taxes, because they're already spending a great amount of their money on basics. (Not to mention that they have to pay sales tax in most cases, which is a regressive tax.)
After all, toilet paper doesn't start costing more for a millionaire, does it? Of course, you have some millionaires who do try to spend/consume up to their amounts (professional athletes come to mind), but many multi-millionaires tie it up in businesses overseas. (Free traders would argue that brings down prices for those in the states, but it doesn't mean much if you don't have a job to make money to buy those goods in the first place...)
I really see no reason that a man of Romney's income can't be paying 20% on his taxes intead of 13%. What I'd like to know, is how many people are actually paying the top percent of 35%? It seems like there's a curve, where as you make more you come closer to the top percent, but as you being to make even more, you have enough disposable income to invest/hire lawyers/etc etc to bring your tax rate down, down, down...