I think a lot of the appeal of this comes from the fact that murder does not exist in the Sims' world: Sims cannot consciously kill other Sims. This is not to even mention the games where the entire purpose of the game is to kill people (every warfare game you can think of). Besides, there are video games where killing people is not really detrimental to game play, and is even encouraged after a fashion (the GTA franchise, the Elder Scrolls franchise).
There are far too many horrible things really going on in the world for me to be concerned about what someone is doing in a video game. I'll be honest and say that I do not find this as shocking as you seem to.
