In northern California an American "cage fighter" allegedly took some tea brewed from psychedelic mushrooms and then became convinced that his roommate was possessed by the devil. The results were not pretty.
Warning: extremely graphic content.
A more detailed and somewhat less sensationalistic account is found here.
I'm not saying that properly supervised experimentation with psychedelics in controlled circumstances is necessarily a bad idea, but clearly there are potentially grave dangers associated with casual use. Like, for instance, having your tongue cut out, your face ripped off, and your beating heart excised from your chest ...
The story does make me wonder if psychedelics played a role in the sacrifices conducted by Aztec priests. The extraction of the victim's heart was a notable feature of these rituals.