Your argument, just like most others are here, is flat. What about the few who enter the upper middle-class or the upperclass by either chance/luck or strictly by hard work. I don't think they go in with evil plans to oppress the poor worldwide. Poverty's the very last thing on a wealthy persons life, he/she won't get involved.
I know if i became rich, i'd do what i can, to the best of my ability to help my brethren. I don't know about you but no matter how much money i have, whether I have a few million bucks or I'm short 35 cents, it'll always kill me to see a hungry little kid on the street begging for change, in the U.S., of all places.