Why Are We Bashing Buffett?

What is altruism? Warren Buffett recently proposed a surtax on the very wealthiest Americans, including himself to help reduce the federal deficit.  (This is a mild version of Obama’s perfectly reasonable proposal to tax family incomes above $250,000, i.e., fewer than 2% of families.) Buffett is being altruistic—the tax will reduce his net income. I always thought altruism was desirable, yet I’ve seen Buffett lampooned in the press.
I suppose one can argue that he’s really doing this to preserve the value of Berkshire Hathaway stock.  (The same argument might apply when I donate blood—perhaps I do it because it makes me feel good, not to help others.) But: it’s a pretty sorry state of the world when someone offers to reduce his circumstances in order to help his country and is mocked.