The loss of innocence can mean so many things though. Some people use it to refer to their child finding out that babies aren't born through the belly button. For others it would mean a cynical take on sex, thinking of girls as slags, an excessive interest in violence.
I think what I would like from my son is what you might call an open-eyed, conscious innocence. Knowing that there are bad things in the world- violence, hatred, disrespect- but also being able to say to himself that I don't have to be part of that. I don't have to speak disrespectfully of other people, I don't have to only see the dirty side of things.
When my son asks me about death, I don't just tell him the facts about the dissolution of the body: I try to show him how we can make a positive difference, how we can support bereaved people in the community, how we can help save lives in poor countries. We talk about the people who work to save others, the firefighters who were risking their lives at 9/11. We talk lovingly about our own dead and how much they have given us.
I may let him watch a censored film if I have watched it first and made sure that it contains nothing that I think is inappropriate. And if it contained bad language, or people behaving badly, we would discuss what kind of a person this was and what made them behave this way.
But I would ruthlessly ban any play-material that encouraged a cynical or disrespectful attitude towards other human beings, as I believe some of the GrandTheftAuto stuff does (not that I have seen it).