Hmmmm...
My take on this is based on the fact that the whining isn't so much about gun-specific games, (I could be wrong about that. I'm not up on the news re: game-bashing.) but about criminal activity-specific games like GTA.
Isn't most of the noise about "glorifying gang-banging" and such tripe? I can't think of any squeaking about most military-format games, or sci-fi-style games like Unreal and Half-Life.
The Sci-fi's and Mil-sims are very popular. Good sellers, for the most part, so long as they're a good game. Gamers are rather picky.
I make this point because of an early-generation first-person-shooter called Kingpin that was directly aimed at the "wannabe-criminal" market. It's premise was about murdering rival gang-members in order to claw your way to the top of the heap, and take over. The game was brutally violent, and had a selection of fairly mundane (Compared to Unreal and the like.) set of weapons to accomplish this. Along with that was a vocal selection of abusive language appropriate to pre-conceived notions of what gang-bangers would say. This was all combo-ed up to make the game appealing to the "criminals are cool" juvenile market that all of the media-hype said was clamoring for violent games, which would subsequently twist their tiny vulnerable juvenile minds into violent killing machines.
Seemingly in the face of accepted facts, the game bombed. Horribly. Despite it's premise, and carefully constructed "live like a criminal" environment, the game utterly failed to catch on in gaming circles. Gamers were unimpressed with lackluster gameplay, ordinary environments, and boring weapons. Unlike media-hyped predictions, the juvenile gamer set was NOT enthralled with criminal activity, they were more interested in cool visuals, kick-butt weapons, and challenging play. This is well-documented on a lot of online game-review sites where ho-hum reviews of Kingpin are the standard fare.
Gamers are gamers. They like to play games. They don't regard games as simulation-training to tide them over until they're big/old enough to go out and wreak havoc on the real world. I think that people who worry overmuch about what kind of effect that lots of gaming is having on a given set of kids are entirely missing what the priorities of said set of kids really is. IMO these kids aren't into what the game's about, so much as how the game plays.
Adults aren't even part of this discussion. They're adults, and are responsible for their own actions. If the question is "Do games de-sensitize kids to violence and/or crime?", I think the answer is no. I don't think that "criminal-format" games are attractive because of their "criminal" element except to adults, who know better, and can be held responsible.
Any parent raising their kids with a set of priorities that regards criminal activity/violence as an achievement shouldn't be raising kids, and that takes us right back to good parenting.
Just my opinion, and like I said, I'm not well-informed on the violence and gaming debate, but I have a hard time assigning any kind of credibility to the argument that gaming encourages violence. I haven't been able to find that kind of correlation among the principles, to wit: gamers don't get frothy about the violence in game reviews, and it takes more than just violence or a criminal premise to get a game to sell well. Kingpin was based on the Quake engine, and Quake was a very successful game, so mechanically, Kingpin was well-equipped to provide good game-play if the rest of the package was fulfilling a marketable desire.
It wasn't. Kids aren't criminals waiting to happen, held in check only by closely-controlling, exposure-limiting parents. Raise your kids to be good kids, and guess what? They're good kids! Surprise, surprise.
Criminal activity/violence is NOT the lowest common denominator for civilised behavior. To assume that it is is selling society short, and equates to fear-mongering, something liberals live for. 'Nuff said.