Call it the Cosby Consensus. Across the country, middle-class black Americans are applauding comedian Bill Cosby's insistent campaign to draw attention to the bad habits and poor choices that limit black achievement. There has been little disagreement about his main points — that drug use, poor classroom performance and the embrace of outlaw culture have done nothing but cement the black underclass at the bottom of American society. An ethic that dismisses serious scholarship as "a white thing" has handicapped middle-class black kids, too. In early September, Cosby spoke at a Washington forum sponsored by the Congressional Black Caucus Foundation,...