I'm pretty sure you're not going to see much of a debate here Punk. You might try taking this to... School or something. This is, after all, a video game creation forum, and the massive majority of video games incorporate violence, the ones created here have no exception. And I'm sure most people stand by their work and say, "playing this won't make you kill people."
Now, I'm pretty sure to an extent, yes, video games do teach violence to an extent. But it's about 1 brick in the side of the local prison. Just like when you see the police beat up a guy that's drinking and making trouble and you think, "good for them," or when you see a boxing match on TV, video games give you a lightened impression of violence. I'd have to say how movies are all trying to make realistic situations more popular are probably more at fault for violence than video games though. I mean, who's going to see Final Fantasy VII, and get it in their head that they need a giant sword. Nobody that's who, shut up. But you see gangster movies, like Scarface (and yes, everybody thinks Tony Montana is cool), and you think, "holy shit, cocaine is a hell of a drug, I'm gonna get me some Cuban buddies and shoot me up some drug dealers and steal their business."
The moral of the story is, of course, that seeing anything leaves an impression. Video games are sometimes very realistic, and leave a greater impression, and sometimes lead people to do silly things. There's no one thing at fault for a person's actions, it's a mass complex of crap leading up to the event. Like Mr. I-Shot-My-Friend-Over-A-Game-Of-Madden. You think it's the football game's fault he shot his friend? Yeah, but only in the term that it was a competition, I'd put more at fault the guy's upbringing as an obvious jackass.