Oprah Winfrey's poke at the short-sighted materialism of some low-income students has delighted conservative commentators, but that doesn't mean she's wrong. Liberals love to "speak truth to power," but the powerless need to hear the truth, too. Knowledge, after all, is power. Don't keep it to yourself, I say. Spread it around. That's why the Queen of Daytime Talk did poor folks a favor when she candidly explained in a Newsweek interview why she decided to build her lavish new school for impoverished teenagers, the $40 million Oprah Winfrey Leadership Academy for Girls, in South Africa instead of the United...