I only had one of my kids interested in these games. I watched once, felt sick and tossed them all, told him "new rule, no games that have you shoot anything that looks like a human."
Bingo! Parents need to shut down the assumptions that go with this "entertainment" early and hard. Well-socialized kids are not an accident!
My 6 year old daughter knows the four rules of safe shooting and to always first unload any weapon she encounters. However, when we visit my in-laws house (serious anti-gunners), they let their kid play FPShooter games and shoot airsoft pistols at other kids. It astounds me.