“I’m not willing to do this anymore,” he says. He leans over, drops his head as if in penitence and pronounces himself riven with regrets. Now, at 53, Beck sees a nation of people who are at one another’s throats, and he blames his language, his meanness and his assaults, his constant selling of the idea that the other side was evil and that his side had the one true answer. He believes that his radio show and his TV shows and his rallies on the Mall paved the way for the incivility, intolerance and general indigestion that now plagues...