I've always ascribed this to simple populism, where the majority being non-rich simply don't mind placing a higher societal burden on a different group, but I wonder if anyone has a reasonable argument about why they deserve to pay at a higher rate that might convince me.
What does 'deserve' mean? How do we define what some deserve, while others don't?
I think there are several compelling arguments, but the top two would be:
1, America is for the most part a europe-descended society, and the experiment of allowing the 'nobility' to amass unlimited wealth and power didn't end well there, in the opinion of the founders of our society. Progressive taxes help fight this phenomena of concentration of power amongst the tiny few.
2, the rich can afford to pay much higher rates without significantly damaging their lifestyle or ability to engage in society. If they aren't meaningfully harmed by the tax rates, there's no reason not to charge them, because we need the money!
If those aren't convincing or worth further discussion, I'm willing to move on to other arguments if you like.