I just want to add this: I don't know wether role-playing violent games increases violence or not. I can imagine hypotheses where it decrease violence as well as increase it. I also can imagine situations where it might have different effects at different ages. Perhaps that's part of what leads to the polarized opinion. What if role-playing violent acts increases violence in children but decreases it in teenagers?

I think the point is to not assume that it is not automatically the same as watching a movie.