John Carmack, id Software's technical genius, has suggested that violent games can actually reduce aggression and violence. Chatting to IndustryGamers, the man behind Doom maintained that the cathartic effects of gaming made for a more peaceful crowd than you'd find in other sections of society.
I really think, if anything, there is more evidence to show that the violent games reduce aggression and violence. There have actually been some studies about that, that it’s cathartic. If you go to QuakeCon and you walk by and you see the people there [and compare that to] a random cross section of a college campus, you’re probably going to find a more peaceful crowd of people at the gaming convention. I think it’s at worst neutral and potentially positive. - John Carmack
Carmack's not alone either. Earlier this year in a preview presentation for Prototype 2, developers Radical Entertainment noted that catharsis was a big reason behind the success of the original game. Empowerment fantasy has been a mainstay of gaming for years. We'd like to see some comprehensive studies undertaken, though...if only to keep Fox News off the industry's back for a little while.