There has long been a debate over whether pornography encourages rape by normalizing misogyny and arousing passions, or discourages rape by providing an alternative outlet for lustful urges. Unfortunately, this debate has generally been religious rather than clinical: instead of basing their positions on data, partisans have created moral edifices around their underlying sense of what should be true.
According to an article in Slate, there is now meaningful evidence that access to Internet pornography reduces the incidence of rape. There is also evidence that violent movies reduce violent crime. Really. Check out the article and make up your own mind.