I've played violent video games since I was 4 or 5 years old too. I recall playing No Russian when I was very young, and although I didn't entirely understand what was going on (terrorist, World War III, etc), I did understand that the level for whatever reason had the character kill civilians, which the game didn't normally allow, and that what the characters were doing was bad, but it was just a video game so it was okay.

My dad has been a big gamer since before I was born, and I was playing a lot of his stuff. He just always told me and my brother that a lot of the stuff in the games were bad, but it was just a video game, so it was okay. I think his idea was that it was better not to shelter kids from the violence/etc in video games and other media and create the "forbidden fruit" type of appeal. I don't know if that parenting method would work for everyone, but it did for me and I appreciate it.

A lot of my high school teachers blamed violent video games for violence in today's society. I don't think they ever realized how many of their students, including myself, were pretty much raised on those video games, and these were the same students those same teachers constantly raved about being such good kids.