I think the problem lies in a different direction. We, as a people, have always had violence in our entertainment. While we have gotten better at graphics, a quick look at the old legends and tales told by generation after generation shows the same violent tendencies. Grim's Fairytales were MUCH more graphic in the original versions, and our heroes have almost always been violent.
But in the past we also had a strong sense of community. We interacted with people in genuine ways. It was far more difficult to dehumanize them.
Sadly, our "communities" are now largely virtual. We have managed to dehumanize each other to an amazing level. So we find it easier to kill.