It is, but there are a few grammatical errors, and a possible usage or word choice issue. "To criticize" usually means "to judge negatively." It would probably be better to say "uncritically." Making that change, and correcting the errors, I would write: "He accepts messages delivered by the media uncritically." Other possibilities would be: "He accepts the media's messages uncritically," or, even more simply, "He accepts the media uncritically."