1) Critic or iconoclast 2) One who exposes a sham 1) Skeptic 
A debunker is a person who attempts to expose or discredit claims believed to be false, exaggerated or pretentious. The term is closely associated with skeptical investigation of controversial topics such as U.F.O.s, claimed paranormal phenomena, cryptids, conspiracy theories, alternative medicine, religion, or exploratory or fringe areas of scien...