In January, almost 2,000 people jammed the auditorium at Wayne County Community College in Detroit in order to hear Bill Cosby yell at them—there’s really no other way to put it—for being bad parents. That was after a crowd had already filled a hall in Newark. And another in Springfield, Massachusetts. And another in Milwaukee. And yet another in Atlanta.Had Cosby not gone into quarantine as the result of sexual-abuse charges that prosecutors say they are no longer pursuing, there’s no question that thousands more poor black parents would have come to town-hall meetings, asking the comedian-activist to harangue them,...