Same reason I don't trust any study about how games can make you violent and crap like that. It's always the unstable that pull crap and get the idea from a media, never a sound minded person. We have no way to protect against all unstable minds, so censorship because of them is just silly.

In this case, study doesn't really work. You would need to do a much bigger scale with people from different areas. There's also the chance the subjects lied on certain things in the study, I know I did when I was a part of a small health food study as a kid.