Give me your best reason for why games such as Grand Theft Auto aren't maniacal.

The arguments I’ve heard are:
1) It’s not real life.
2) It releases you from reality and allows you to vent.

I understand that a lot of video games involve killing, stabbing, squishing, and cutting bridges under bowsers, but Grand Theft Auto (GTA) is very realistic and detailed, so this adds a whole new dimension.
I’ve played GTA before. Aside from the heinous acts, it’s a really cool game and the visual designers are geniuses. I loved driving around in a truck and exploring all of the neighborhoods of mock-LA while listening to the awesome radio. I could spend eons doing that, but I wouldn’t want to approach innocent civilians, steal their cars, and beat them to death. Do many other people not feel this way?
So if you think it is maniacal, then why is it so commonly accepted in society? If I told people I sit in my room and stab a doll with a pencil, they would probably recommend I get psychiatric help. But perhaps I’m comparing apples to oranges here. (Please don’t assume I stab dolls with pencils—I don’t)
To be clear, I’m judging the game, not the people who play the game.