The controversy makes the game so popular, aside from the greatness it contains. Everyone wants to be a rebel and play the big kids' game. As long as they are not held back by laws they will continue (in a half reasonable fashion) to tell people like Jack Thompson to off, while avoiding law suits.
I think this game doesn't promote violence, rather promotes natural selection. Even as a little kid you should have some common sense to know whats unacceptable from gta, if you don't then blame it on the parenting.