Harold Schechter did not have a killer time watching “Monster: The Ed Gein Story.” Schechter, a true crime historian and author who wrote the definitive book about Gein, “Deviant: The Shocking True Story of Ed Gein, the Original Psycho,” told The Post that he’s unhappy with the third season of Ryan Murphy’s anthology series, which focuses on Gein and his crimes. “Ever since I heard that Murphy was planning to make Ed Gein the subject of his third season, I have been feeling aggrieved and