Because men get to look at beautiful women as their desire, whilst women have to put up with hairy arsed men, and so have less likelihood of finding that great ?
Or, of course, it could have either nature or nurture reasons. Perhaps the way the brain is wired encourages more interest in relationships than visual images of the body ?
As for the "degrading" opinion I suspect one has to first decide one is not keen on porn, and then project how they would feel across the board and think others with a different view are doing something bad. It says more about those holding such views, especially those who act on them, than it does bout porn itself.
Plus I suspect such individuals have the opinion that porn means men doing things to women rather than individuals doing things to themselves or holding an equal responsibility/whatever in a situation. Maybe they thing men couldn't degrade themselves no matter how they tried :-) Which would be a rather sexist viewpoint if it turned out to be true. But there again that's the way life is.