You must really hate Game of Thrones then (or any other type of fiction that depicts this topic). First, it's not real and all fantasy (which is fine). Second, how about all the games were you go around killing and murdering people? That could be considered sick as well and yet that is considered perfectly fine (most of the time), because NONE of it is REAL! Get what I'm trying to say? Playing this game does not make me want to go out and bang my real sister, just as playing a shooter doesn't make me want to go out and kill people.
And as khairus mentioned, if you don't like it, then don't play it and move along to stuff you do like. It's really that simple.