I think sex is just different from violence. Violence is something quite pulic. Sex is not. It's intimate. Also ~violence, not day to day drive to harm or kill people, just ability to attack for defense, is almost a desired skill. If you don't do that you'll be stepped on. If not physically, emotionally. So displays of violence is almost pedagogical. Reminds me that, as a kid, Japanese animated show were censored heavily because it was fights with blood.. but the warriors were always defending (fist of the north star, saint seiya,...). There was no psychopathic desire for aggression there.