Start here, with a semi-skeptical take, and follow the names to the researchers websites and to SCHOLAR.GOOGLE.COM. There's controversy, but this isn't fringe science.
What do you mean by fringe science? The authors in that wikipedia article claim most studies have been flawed, and even their own can't show causation.
I also still remember being a kid, which gives me a somewhat biased opinion, I guess.
My own non-scientific guess would be that peer pressure is more important. Personally I was never much into watching gruesome movies, for example, but for a while it seemed to be a test of courage among other kids my age. So essentially kids might have been watching more gruesome stuff than they really liked because of peer pressure. Or they really liked that stuff - then I wonder why?
Also as kids we loved Wild West stories, would dress up as Cowboys and Native Americans and shoot around with toy guns. The totem pole and the associated torturing were a particular favorite. We never mistook play for reality, though (no real torturing).
Yeah, me too, but that didn't happen when you were FOUR, right?
Let me disclaim right here that the kind of bad parenting on display in this article is of approximately the same valence as the bad parenting I inflict on my kids on a weekly basis. I'm just saying it made me queasy is all. The kid, who is clearly awesome, is going to be fine.
http://en.wikipedia.org/wiki/Grand_Theft_Childhood