Eh, some people are just predisposed towards violence, irrespective of where it stems from the majority of the time. You'll find that they had plenty of other signs in their life that something wasn't quite right well before WoW even came along into the scene.

Besides, the reason that people are so quick to blame video games over something more mainstream like movies is because they want some sort of scapegoat that they couldn't care less about if the industry falls over, because they don't play them. Not their precious entertainment, no way can tv or the movies ever influence anyone. /sarcasm