If you debunk a widely held belief, you show that it is false. If you debunk something that is widely admired, you show that it is not as good as people think it is. Historian Michael Beschloss debunks a few myths. to show that an idea or belief is false (BUNK2)
expose while ridiculing; especially of pretentious or false claims and ideas; "The physicist debunked the psychic's claims