Fairness and hard work
That's what we believe that it takes to succeed in this country. Sometimes this makes us willfully blind to unfairness (that person must be smarter, harder working, better in some way than we are because he has a better job and a lot more money). But while we expect things to be fair and we expect hard work to pay off and we are willing to go to great lengths to rationalize the world as it is, it's still becoming increasingly clear that what we see right now in this country is that neither of those things hold.
Jeanne D'Arc has an excellent post on this topic:
Most Americans are genuinely patriotic. They want what's best for their neighborhoods, their cities, their states, and their country. And taxes are our contribution toward making it work. At one time we believed that the more you received from the country (and rich people obviously get enormous benefits from living in this country; if they didn't they wouldn't be here), the more you owed it -- and as a result we had a genuinely progressive income tax.
Whittling away at the middle class as we've been doing for a while now and as Bush, et al, do continuously and agressively hurts our stability, our generosity, our clear-sightedness and ultimately our sustainability. The rich do not make this country great. It takes all of us to do that.
She cites an article by John Balzar which is also worth tracking down.