It should come as no surprise that fundamentalist Christians are opposed to pornography. Unlike LGBT issues, which Jesus did not mention at all, Matthew 5:28 is pretty clear: "But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart." Technically, "adultery" only applies to those who are married, so it might not be sinful for a single man to view pornography of a single woman, but that would be seriously splitting hairs.
Even though I personally find such repressive religious worldviews kind of silly, in the end there's nothing wrong with practicing your religious beliefs as you see fit. It only becomes a issue when you try to use your religious beliefs to restrict the lives of others who don't share those beliefs. But basically, the problem is that a lot of fundamentalists are seriously bummed out that non-fundamentalists can look at whatever they want.
The fundamentalist establishment decided that the only solution to this problem was to ban pornography for everyone, and in order to do that they needed to show that it was somehow objectively harmful. First they tried "think of the children!" initiatives like the Child Online Protection Act, but those failed. So more recently, they have been pushing the concept of "porn addiction" - which, as this article from Salon points out, probably doesn't exist.
“You see, your brain comes equipped with something called a ‘reward pathway.’ Its job is to motivate you to do things that keep you and your genes alive — things like eating or having sex to produce babies,” the anti-porn site Fight the New Drug argues. “The way it rewards you is by releasing dopamine into your brain, because dopamine makes you feel good.”
The notion that feeling good is suspect should be a reader’s first clue that this site is dealing more in conservative Christian propaganda than science, but I reached out to an expert, Dr. Nicole Prause, for a response to this argument. Prause, a scientist who started the research firm Liberos, has done research that turned up no real evidence for porn addiction.
“Sex films are rewarding,” Prause explained over email, “and there is greater activity in dopamine associated with learning rewards (not pleasure) when people view sex films. However, the same could be said for watching puppies play, and we do not call puppies addictive,” she added.
To be clear, no one denies that there are people who act out sexually in inappropriate ways, or whose sexual behaviors are compulsive to the point of being destructive. (Everyone watching this week’s edition of the ongoing Anthony Weiner saga can see that with their own eyes.) But that doesn’t mean that the behavior should be classified as an addiction, which is one reason that various editions of the DSM have rejected porn or sex “addiction” as a legitimate diagnosis.
“We have ruled out addiction,” Prause explained. “The three best candidates at the moment to explain these behaviors are: high sex drive, social shame (i.e., behavior is normal, but they are shamed for it), or compulsivity,” any of which requires “different predictions from addiction models and would require different treatment approaches.”
I'm going to repeat this because it's super-important and people keep failing to see the significance. There is such a thing as compulsive behavior. It ranges from having to flick a light switch five times whenever you walk into a room to acting out sexually in extreme ways. But it's not an addiction, and you can't treat it like one. There's no evidence that addiction treatment methodologies work do anything for compulsions. Usually treatment requires some sort of medication, because the brain's conditioning system is all haywire and that's what's producing the behavior.
There's also no evidence that pornography exposure causes people to "build up a tolerance" to it and need "harder stuff." As the article points out, fundamentalists like to argue on the basis of the addiction model that developing a tolerance for adult porn leads people to seek out child porn, but that's nonsense too. Pedophiles are attracted to children, and are the only people interested in child porn. Normal adults don't find children sexually attractive at all, and no matter how much adult pornography they watch, that's not going to change.
And as a point, the abuse-tolerance-withdrawal model doesn't even work with a lot of drugs. It was primarily developed from studying alcohol and opiates, which do behave like that for chronic abusers. But if it doesn't even work for the majority of drugs, how much success would you expect it to have when applied to conditioned behaviors? Here's a hint - the biochemical effects of opiates and alcohol are not caused by a "depletion of dopamine receptors," though that can be caused by different drugs that attack on the receptors directly.
All of the arguments for the "porn addiction" model are straight-up pseudoscience, and keep in mind I'm saying that as a sorcerer. Unfortunately, a lot of people have been taken in by them, and not just fundamentalist Christians. There are number of otherwise very liberal folks who buy the fundamentalist addiction model without applying any critical thinking to its tenets, and thus find themselves allied with conservative Christians on this issue. But the model needs to be questioned with real research, and every time somebody runs an unbiased study, the results do not support it.
Given all that, there really is no utilitarian argument for banning pornography created by consenting adults for consenting adults. So it's entirely a religious issue, which means that it should never be enacted into law. Is it really so hard to just refrain from viewing it if your religion prohibits it? Why should anybody else's consensual sexual behavior be your business? If we can ever get these folks to the point where they understand this simple principle, the world will be a much better and happier place.