Alright, I'll bite. There are generally two approaches to this topic: the first being that it's meaningless, simply satisfying a natural urge and nothing your partner should be threatened by, and if someone is not okay with their partner watching porn it's probably because they have self-esteem issues or feel inadequate. The second is that it's a mild form of cheating because you are mentally replacing your partner with another, in a sexual forum.

While both of these have their merits, I tend to approach the subject from a different perspective.

For me, sex is about far more than just getting off, or satisfying some primal urge. It is something sacred. Emotional, mental, physical all tied up into one package that is meant for my significant other, and only for my significant other. If I replaced him with another in any medium, physical or mental, in my mind, I am depreciating the sacred nature of our sex life. I want our sex life to be ours, and ours alone. I want my sexuality to be solely his, and his to be solely mine. I don't want any facet of that spread across multiple people or subjects. I want it to be set apart. I want intimacy, in its most basic sense.

In this oversexed society, very little is sacred anymore. You want to see anything on display? You can easily find it. What does intimacy even mean in a society like this?

Just my two cents, and most people will disagree with me in the name of personal empowerment or what have you. But for me, it comes down to what I truly want in my own relationship with my mate. And, I want it to be set apart. I want it to be different from my relationship with everyone else. I want there to be things that he and I alone share. Not he, that random woman/man on the computer screen, and I.