Just 400 families in the US saw their wealth increase by $670 billion in the first seven years of the Bush Administration!!! Of course, that's not "class warfare" when the distribution get concentrated upward; that's just "free enterprise" at work. And Hannity complains that the rich pay 70% of all the tax revenues.
1) I would suggest that this widening of the wealth gap is not about income taxes and thus income taxes will not fix it. It is about structural problems in how compensation is created in the US. I would like to see this wealth gap shrink because it is both bad for a democracy and indicates a probable disfunction in the rules of our economy (i.e. inefficient allocation of resources). Sadly I think the chances low that anyone in power will understand anything other than the simple tax-the-rich bandaid.
2) I would likewise suggest it is dangerous in a democracy to have one class paying too much of the taxes. It engenders the attitude of we can buy anything because the other guy is paying.
3) If you use the income tax to level the playing field it DOES have consequences - e.g. I can remember my parents intentionally investing in money losing propositions just to avoid a 70%+ income tax rate. It makes no economic sense - but it is what a huge segment of the those in the top brackets were doing. And in other countries the uber-rich have just up and left.
None of this is to suggest that I object to a small increase in the top brackets - but lets not assume this somehow fixes the problems.