Religious people don't only believe that porn harms the models, but also the user. I happen to agree, despite being a porn user - Porn is a form of simulated and not-real stimulation. Porn is harmful to the user the same way that any form of delusion is: It associated positive pleasure with stimulation that does not fulfil any basic or even higher-level needs, and is unsustainable. Porn is somewhere on the same scale as wireheading[1]

That doesn't mean that it's all bad, and that there's no recreational use for it. We have limits on the availability of various other artificial stimulants. We should continue to have limits on the availability of porn. Where to draw that line is a real debate.

[1] https://en.wikipedia.org/wiki/Wirehead_(science_fiction)