It think this discussion needs evidence.
Show me a graph of shootings, violent games and population against time.
(accepting that correlation!=causation)
Then I can form an opinion on the potential dangers of GTA.
I do not have it on hand now, but the link between video game violence and real world violence has been thoroughly disproven time and time again. It is no more than a few months ago that another far-encompassing meta study was released, with the same conclusion as every study before it: There is not even correlation between video game violence and real violence, let alone causation. That is what science tells us. Just as with Jazz, Rock'n'roll, Comic books and Role-playing games before it. And, much the same way, loads of "concerned parents" are ignoring science in favour of their own common un-sense.
Why is that? Wouldn't people be happy to know that no, the fact that your kid is playing video games is in no way predisposing him/her to actually shooting people up when he's a teen? Well...It usually goes the other way. Why
do kids turn out violent and asocial? What creates a school shooter? Usually, when you look at it closely: Bad parents. Kids do as their parents do. If the parents are violent and asocial, the kids learn to be like that. If the parents are vocal about shooting people as a solution to their problems (even hypothetically - That is "I have this gun here, and if someone comes onto my land I'll shoot them"), then the kids will learn that, too. The absolutely most significant correlation (and likely causation) for kid behaviour: Parent behaviour.
Now, when do people start looking for an "explanation" for a violent kid? When something bad has happened. When little Billy has gotten dads guns from the cupboard, gone to school and solved his bully problem permanently. And what kind of explanation do people want to find? Well, they sure as hell doesn't want to learn that they (if they are the parents) made little Billy like this. Or (if they are the neighbours) that Bud and Daisy made little Billy turn out that way. After all, in most cases, people in a close community are rather similar in outlook and values - If Bud thought that shooting at "foreign" intruders was a good idea, there is a good chance that his neighbours think the same. That's just reason - Surely that is no harm? So, where shall we put the blame? In something external - Video games, nowadays. Roleplaying games, 20 years ago. "N*gger music", 60 years ago. Anything that means it is external, that means it is not
our fault.
So, there you have it
Video games does not cause violence. Science says so. If you really want, I can drum up a dozen links or so to scientific reports, but you really should be able to find them yourself with a small effort.