I've had these sort of conversations with my parents, and so did my brother when he lived at home. But my Dad won't have any of it. I'd like to feel I'm a lot more mature and understanding of the world than a lot of people who play these games, and yet I'm not allowed them. My Mum has no problem with it, and claims I'm 'old enough and ugly enough to understand this is irrelevant to real life and you can't go round shooting random people and not suffer the consequences'. While my Dad claims he feels the same way. But why can't I buy them? Who knows. It's one of the great mysteries in life :p
Having said that, I can't see the excitement in wondering around and shooting random people for the hell of it, but that could be because I've rarely played these games. And I'm not an avid gamer anyways, so I'm not actually that fussed *shrugs*