Young people have been running amok at Sacramento showings of "Coach Carter," the Samuel L. Jackson film about a Richmond basketball coach who straightens out wayward students. Rachel Kahan was at a Century Stadium 14 showing on Arden and Ethan when a riot broke out. "Kids were beating up a security guard, and they attacked the manager," she said. "It was awful. And what makes it worse was that the behavior was exactly what the character Coach Carter is fighting against." Other showings have been disrupted by shouts and threats from boozed up fans. Paramount Pictures, which distributes "Coach Carter,"...