The Virgin Killer's manifesto actually describes how he was emotionally traumatized by porn at a young age...
"Towards the end of sixth grade, I still hadn't made a group of friends who I could see outside of school. ... Joining chatrooms through AOL temporarily filled in the social void for a few weeks. This will definitely not be the first time I would try to fill in that void with the internet...
One friend who I met through a chat room suddenly emailed me pictures of beautiful naked girls, telling me to "check this out". When I looked at the pictures, I was shocked beyond words. I had never seen what beautiful girls looked like naked, and the sight filled me with strong and overwhelming emotions. I didn't know what was happening to me. Was it the first inkling of sexual desire in my body? I was traumatized. My childhood was fading away. Ominous fear swept over me, and I stopped talking to that person.
As the Sixth Grade year came to a close, I felt dissatisfied and insignificant. Indeed, a whole new world had opened up before me, and I had no idea how to prevail in it. I still wanted to live as a child."
"One time while I was alone at Planet Cyber, I saw an older teenager watching pornography. I saw in detail a video of a man having sex with a hot girl. The video showed...(deleted). I didn't know anything about sex at the time. I barely even knew what sex was. I was slowly starting to develop sexual feelings for hot girls, but I didn't know what to do with them. To see this video really traumatized me. I had no idea what I was seeing... I couldn't imagine human beings doing such things with each other. The sight was shocking, traumatizing, and arousing. All of these feelings mixed together took a great toll on me. I walked home and cried by myself for a bit. I felt too guilty about what I saw to talk to my parents about it. I was quite shaken for a few days.
This was among the very first glimpses I had of sex. Finding out about sex is one of the things that truly destroyed my entire life. Sex... the very word fills me with hate. Once I hit puberty, I would always want it, like any other boy. I would always hunger for it, I would always covet it, I would always fantasize about it. But I would never get it. Not getting any sex is what will shape the very foundation of my miserable youth. This was a very dark day."