There is clearly a difference between violent and degrading pornography, and other forms of sexually explicit material, but it's not simple.
First, I would direct your attention to the fact I have conducted experiments on violent pornography. That type of pornography has not been absent either in my experimental research or in my correlational research, where I found that people with a high sex drive tend to use more violent pornography than people with a low sex drive. I conducted a study in which men were given electrical shocks and verbally harassed by a female and then shown violent pornography. We showed them classic violent pornography taken from the classic research and then we gave them an opportunity to be aggressive or not to be aggressive, by talking to the woman, or whatever. There is a difference.
I want to direct your attention to two other things, though. There is a community of folks—and we have no idea how large it is—who refer to themselves as into kink, bondage and discipline, sadism and masochism. It is one of the most completely consensual communities around. They could give us lessons on how to obtain consent, and they exclude people and ostracize them if consent is violated. There is a substantial amount of BDSM pornography or sexually explicit material that you might argue is an area that doesn't exactly conform to violent pornography.
Classic violent pornography, the lie of violent pornography—which is happily not too common but is definitely problematic—is that sexual assault works for him, because he gets sex and works for her, because she has an orgasm, and nobody gets punished. Okay? That's an advertisement, if you will, for sexual criminality. However, don't be of the school that views pornography from a monkey see, monkey do perspective. Generally speaking, the monkey has a learning history. Generally speaking, the monkey has a brain, anticipates punishment, anticipates guilt, and if the individual is very unempathetic, doesn't have a learning history of punishment, etc., then we've got big problems.
There may be big problems with pornography in a confluence model context. It may be a big problem with almost any other script for aggression, and we do not lack them in our society.