I'll use a small quick example to explain why the percentages used here aren't the best way to try and represent the situation.

Lets say there is a flat tax of 10% of income. Bob has an income of $100,000. Joe has an income of $1,000,000. So, at 10%, Bob pays $10,000, and Joe pays $100,000. Using your stats above, indeed this can slant things to make it seem like Joe is getting really screwed over, when both are paying an equal portion of their income. Because in this situation, Joe is paying close to 90% of all tax income of the example, and Bob is only paying around 10%.

Of course the citizens who make more money are going to be putting more money into the tax system then the poorer citizens. The question is, at the end of the day, is it fair what either group is paying? And is that money going towards improving the country as a whole, allowing for greater chance of success for all? While Republican values may be for smaller government and Democrats may be for bigger government, there is a balance in there somewhere. Too little, and those highways vital to the trucks moving your widgets around to sell fall apart, thus impacting your business. Too much government, and too much of peoples income goes into the tax system, not allowing people to justify buying those widgets.