This is an excellent article from (Henry Jenkins – MIT) – even if I only say that because it supports my own experience and instinct (plus bias!). In (crude) summary: games are not just for male children, they are social and there is very little evidence that they encourage violence among the young, except that violent play may lead to violent play. Sort of obvious when you think about it. There is more to the article than this and it is good to see such a clear and reasoned debunking of these commonly believed myths.
If would could save all the money wasted on poorly designed violence-in-games research we perhaps we could put that into more proven contributors to youth violence!