When Mr. Devlin discovers Fred in his kitchen, Fred, all of a sudden, goes from being uptight and worried that Devlin is a cannibal to calming down and eating Devlin's food.
During the first half of the movie, Fred believes that Devlin kills and eats people even though Devlin lives in a densely populated neighborhood for most of the movie. It is highly unlikely that Devlin would be safe from the law if Fred's allegation was true.