Just as with everything else in the world, it isn't so black and white. There is truth in that the easy access to porn can fuck with your sexual desires. People who consume porn a lot tend to grow tired of watching the same thing over and over and will seek new and thrilling material. There's nothing inherently wrong with that, but I can imagine that leads to problems with your real sex life. Expectations get higher, you might crave certain things to get off because you've grown more or less numb to other things. There's also that whole thing about how women are often treated in porn. Most of it is in good fun and a lot of women get off on it as well, but consider that young guys who haven't even had sex with a woman yet avidly consume this type of porn. On the other hand, just as with violence in movies and games, I strongly believe that people who act out violent fantasies and seriously harm others were wrong in the head from the start and violent media in itself is not to blame. But there's also a lot of pressure on young girls to act a certain way and be ok with certain things. Couple that with piss poor sex education pretty much everywhere in the world, where kids often have to learn what sex is supposed to be like from porn.
At the same time, people need release for their sexual desires and I think not getting that release builds up frustrations that will fuck with your head and might lead to you doing some bad shit. I don't know, like I said it's not so black and white. One thing I'm sure of however, and that is that people are very different and some have an easier time distinguishing between fantasy and real life than others.