I'm the last person to get on the video game paranoia, but my belief in art (however you categorize it) and it's ability to teach, touch and change things compels me to acknowledge a 'darker' side to the ability for it to lift us up, or to allow us to realize the 'contingency, irony and solidarity' that we so badly need. In the wrong time, the wrong place, without the proper contexts of age, or experience, these things can convey the wrong message. Imagine Starship Troopers (the movie) if you didn't have any idea that there was a strongly ironic side to it, if you didn't have the ability to draw a parallel between the crazy "Do your part" videos and the propaganda of an earlier age (or not so earlier, "See something, say something"?).
I know it's a thorny issue, but for me it comes down less to studies but to the question of why video games seem to have an exceptional space that TV, movies, books and magazines don't have, where there's a willful blind spot as to the content. When we played on the Atari 2600, maybe it wasn't such a big deal, but watching a death scene from Tomb Raider (the reboot) it suddenly seems very important.
We have a real problem with video games, we're in some kind of a transitional state that I feel many parents are reflexively ignoring or demonizing. It doesn't have to be that binary, same as movies: you probably wouldn't let your 10 year old watch a graphically violent movie with high doses of cruelty and a generally pessimistic outlook on humanity, no matter how classic or great it was. It's simply not appropriate. Same thing goes for video games. Check the label, read a review. Better yet, play a demo.