Actually, the fact that the murder and rape rate has DECLINED rapidly at the exact same time as:
1) Easy availability of internet porn has exploded
2) Introduction rapidly increasing popularity of violent video games
3) Popularity of Gangsta Rap, Death Metal, etc. has increased
Is an awfully inconvenient embarrassment for a lot of people for axes to grind, from across the political spectrum.
Yes, and one could use that data to form a hypothesis that people with tendencies toward these violent acts are using the porn, violent video games, movies, etc, as proxies, to satisfy their urges without resorting to crime. Serial killers are the terminal end of a psychological spectrum of sadistic sexual criminals, where their violent urges are tied to their sexual impulses. Normal men often redirect their healthy sexual urges in various ways, such as exercise, sports, hobbies, and, horror of horrors, masturbation and pornography. There’s certainly good reason to suspect that sexual sadists can redirect their abnormal urges in the same ways. It would explain why most serial killers collect trophies, return to the scenes of their previous crimes, watch pornography, and often try to get jobs where they are in some position of authority. Many serial killers have flat out said that they use these substitutes to postpone their urge to kill again.