I think as long as the viewing of pornography does not hurt anyone (the performer, or the viewer) in any direct way I don't think it is a problem. Obviously, if it becomes an addiction then it is a problem, like an other addiction. But I think everything in moderation.
There is no moderation with this. Trust me, its an addiction. People say, oh I will try a little pot, its harmless after all. They do it and they like it. Now when something bad happens or they are stressed they remember that the pot felt good and they do it again. This keeps repeating and escalating exponentially until they become addicted.
Trust me when I tell you that porn is the exact same thing. Also food addiction. There are many of these addictions, with things that seem harmless. It starts as a reaction to not having a GF or BF. You say to yourself, well God made me to be married by my mid 20's, so what can I do. My body wants it. So I give my body what it wants.
But then very soon you NEED it like you need food. And when stress and problems happen in your life, you tend to waste hours and hours on it, which actually makes your problems even worse because you don't do things you are supposed to and wonder where the time went. Its a vicious cycle of hell.