i don't think it's something that studies can really prove or disprove. however, i personally don't believe something like that has no impact. and even if 1 person out of the 100,000 who bought the game ended up being influenced by the game, it would be 1 psychopath too many. would he have become a psychopath anyway? who knows.
and again, what studies? there was just a study that came out today about how kids who watch too much TV eventually have attention deficit issues. i don't see enough video game studies.
the Wii is an epidemic.