I started to check references so that I could give a good critique but then I woke up to the fact that this isn't my field and I'm not writing a research paper.
So, I'll just go with their conclusion about desensitization:
So, desensitization occurs with even brief exposures to any media violence but we don't have much evidence about the effect on real violence.
Since I'm assuming they know their field, I'll admit that desensitization occurs with violent games.
I can't reach that conclusion based on that, myself. I can accept it as evidence, but not as proof necessarily. We can just as easily cite professional opinions suggesting that while violent videogames
may desensitize people to violence, a biological or psychological predisposition distinct from videogames makes it far more probable for violent behavior to emerge.
Individuals high in hostility are more likely to become aggressive when exposure to violent video games, whereas individuals low in hostility are less likely to become aggressive when exposed (Gentile, Lynch, Linder, & Walsh, 2004). This may lend some insight into the differing theories on the causes of antisocial behavior. Individuals high in hostility have a biological predisposition toward antisocial behavior and, under given circumstances, will learn these behaviors.
Peer commentary from http://www.personalityresearch.org/papers/kooijmans.html
I think an important point people quick to blame videogames for societal problems (not saying that's what you're doing mind you; but there are people who do) may be missing, is that there are plenty of children who play violent videogames practically from birth on, who do not end up being violent, antisocial, or comfortable with violence. So if there is a correlation with videogames, they
cannot be the sole causative factor. If they were, then on their own, with no other factors, they would be sufficient to provoke violence, antisocial behavior, and desensitization in anyone.
Like I told the OP, I've been playing videogames (not to mention seeing violent, gorey movies) since I was 7. Hard to say actually when real violence came into the picture in games. I guess when I was about 11 or 12. But I have played A LOT. I'll be 30 soon. I'm a pacifist because of the principles my parents instilled in me. So what is the difference between me and these other people who are supposedly being made violent by being desensitized through videogame violence? And if there is a difference, doesn't that imply by its very nature that videogames alone cannot be the sole or even primary causative factor?