Guy here.

I'm 19, and given my age and biology...lol well, perhaps a bit of a connoisseur?

I think porn in a relationship is okay, but it has to be expressly agreed upon by both partners as okay. It has the capability to make one partner insecure or otherwise upset if they feel that it is a form of infidelity, which I think is rather understandable. I personally stop viewing porn whenever I'm in a relationship out of respect to my partner, though I don't look down on those who don't. It's ultimately a matter of communication, like most things tend to be.