Parents do need to control what media their kids take in--but not because kids will become more violent if they play Street Fighter II or World of Warcraft. They need to control it in the same way that they shouldn't let their kids watch seven hours of Happy Days all summer long. That is, if someone is going to make decisions about what a kid is taking in, it's should be that kid's parent. I believe there are some major benefits to many video games, movies, and television shows--as Steven Johnson points out in Everything Bad is Good for You--but I certainly don't think any of that media should raise a kid.
But I do see the interest in trying to find a link between video games and violence. I do think that it's worth studying "whether exposure to video-game violence is one risk factor for increased aggression," as the Slate article suggests. As big of a fan as I am of violent movies and violent video games, I'm a bigger fan of not having people kill each other. I think that if legitimate studies can consistently find a real connection, people should take that into account.
In the meantime, I wouldn't let my ten-year-old son play Grand Theft Auto, but I would let my high school-age son play it. So take that however you want.1
1One other thing I'll be doing in the meantime is not voting for Hillary Clinton and her anti-video game-agenda-having ass.