I don't think that you can blame violent children on anything except the parents.
My parents made it very clear to me from an early age that violence and killing were wrong. I have managed to hold on to those values, despite regularly listening to Marilyn Manson, Korn, Slipknot, etc. from my early teen years, as well as playing many violent games - GTA2, GTA3 and GTA Vice City spring to mind immediately, as they have probably been more accused than any other games. On the shelf immediately behind me, I have all of those, as well as MOHAA (+ Spearhead, Breakthrough), Operation Flashpoint (+ Red Hammer, Resistance), SWAT 3, SWAT 4 (+ Stetchkov Syndicate), Splinter Cell, Splinter Cell Chaos Theory, Full Spectrum Warrior, Hitman 2, Max Payne and Brothers In Arms. They are all violent games, but I have never felt even the slightest violent tendancies. I have also never felt compelled to steal a car, or go and destroy an alien race [Starcraft, Dawn Of War (+ Winter Assault, Dark Crusade), Prey], or get on a skateboard and grind on cars [THUG2].
I blame the parents.