The subjective storytelling and flagrantly unreal atmosphere make what might otherwise be an unbearably gruesome spectacle not just tolerable but fascinating, at times weirdly stirring, in the way that a depressing opera or brutal fairy tale or Greek tragedy can be stirring. “Hannibal” showcases the most hideous violence ever seen on commercial TV — some of the murders and mutilations make the ghastliest stuff on “True Detective” and “The Following” seem mild