Does violent media really cause violence, or is it at least not good for children?

I saw porn when I was a kid, and I saw GTA gameplay videos on YouTube, but I was not a pervert or violent maniac like my friends, and they hadn’t even seen half of the stuff I had. In fact, porn taught me how stupid porn and the urge for sex was, and as for GTA, how stupid the characters in GTA were, and criminals in general. So did it really mess me up, or not…?