Here's an excerpt from a good piece on Tim Sandefur's blog:
Liberals believe that government can efficiently allocate resources, and run, say, a health care system for hundreds of millions of people, despite the basic failures of such systems in other countries. And they believe this, not because they disagree with the discoveries of economists like Friedrich Hayek, or have an answer to the problem of rent-seeking, a term which most Democrats have probably never heard. No, they believe this because of their emotional commitment to wealth-redistribution, a commitment based on a moral premise—that the wealthy should pay the bills of the poor because poverty is “unfair”—which they rarely even bother to defend. Ask why your earnings should be taken from you by the state and given to someone else, and you will rarely get an intellectual answer. I’ve certainly never been given one. I’ve heard a lot of emoting, and a lot of accusations of nefarious corporate meanness, and a lot of heart-rending stories about how hard it is to be poor. But an intellectual defense of redistributive government? That’s a rarity.