There are a ton of studies and literature that will tell you that violence in video games is bad for children.  There is very little proposing the opposite.  As a life long game player with zero violent tendencies, I have always found this confusing.  This is the best article I've ever read about why violence in video games is not the end of the world:

Reality Bytes: Eight Myths About Video Games Debunked

The website that's hosting it is PBS and the author is a professor at MIT, which is a nice bonus.

Thanks to The Inquirer for the link.