I have seen more fights (and even heard of a shooting) over games of Madden than any FPS game ever created. That said, I don't think games in general encourage violence and instead are a release in the same way that the Olympics were supposed to be a substitute for world wars. Perhaps games have caused me to lose my empathy over tragedies I hear about in the news, but they have in no way affected my compassion and sensitivity to violence in my everyday life. Ultimately, questions like these come down to the person you're talking about - everything from books, to speakers, to movies and TV (basically all forms of media) have been blamed for encouraging negative behavior, but in end it all comes down to the individual. After all, whatever power those sources may have, they pale in comparison to a friendly or authoritative voice, especially if it's in your own head.