I think a distinction needs to be made between the upper middle class 150-400k a year (depending on location, children and obligations) and the rich, ultra wealthy, .5%, whatever you want to call them. The people that compose the upper middle class work for their income, likely spent long parts of their life in school and even longer working on their careers. The work incredibly hard and are relatively well compensated for it. They also paying huge amount of taxes. It can understand why it is frustrating for someone who has been grinding for 30 years and finally making money seeing 30% go to the government, or to those who don,t work.
However the ultra rich make the majority of their income off of capital gains, dividend distributions, bond payments, attending board meetings. They do little work for their millions and instead have been fortunate to be born close to capital. They have enough money to live comfortable lives without lifting a finger taxed either at 15% or 50%. There is no good reason why capital gains shouldn't be taxed the same as income. The fact that capital gains (income from not working) is taxed at a lower rate than ordinary income (from working) is demonstrative of how the system is messed up.