I agree that the rich should be philanthropic, but living in America not only gives them the right to earn/inherit/win their money but it also gives them the right to keep it and spend it any legal way they want. Think about it. How many of you smoke or drink? Why shouldn't you give that money to the London bombing victims?
Why... Because it's your right to smoke and drink just like it's Chevrolet's right to try to market their stupid Corvette in the All-Star Game where the audience demographic fits their target market.
Take away any of these rights and this wouldn't be America.
As far as taxes. Here's an interesting article on how taxes work. It's extremely simplified and generalized, but the basic jist of it is pretty accurate.