While not a fan of the "rich don't pay their fair share" camp, I find it slightly disingenuous for my side to argue that the rich pay too much. One statistic bandied about is how the top 1% of income earners contribute nearly 40% of federal income taxes and how the top 50% pay almost all federal income taxes. Well, color me stupid, but so what.
Let's say Rich Guy III makes $1,000,000 and Poor Joe makes $10,000 and they both pay 10% of their income in taxes. Well, even though the individual percentage is the same, Rich Guy III will pay $100,000 vs. $1,000, or 100 times the amount in taxes. As a fraction of the tax pie, Rich Guy III pays about 99%.
The Right seems to think that because these percentages are so skewed in favor of the rich that it will elicit sympathy. Wrong, it simply points out that these people are rich and furthers resentment from those who don't make lots of money.
The issue with taxes is not how high they are, but how they incentivize behavior. Rich and poor alike work and invest to make money, not to pay taxes. At some point, high tax rates act as a disincentive to produce. That's a bad thing. Taxes are a means to generate revenue, and revenue consists not only of what you get today, but what you get tomorrow as well.
The winning argument for conservatives is that taxes are too high because they generate lower total revenue. Not that the "rich" pay too much. The reality is that most Americans are envious and resentful of the "rich". To win, we must acknowledge that and adapt.