The issue has nothing to do with what two consenting adults are doing. The issue is how pornography affects society's perception of women. If pornography promotes violence against women (something some people claim and have studies to support), then what those two consenting adults do on film very much affects ALL women.
There is sense in what you are talking about. But there is also much porn which promotes violence against men (some men like this). Does it affect society's perception of men? Is it good or bad?
I'm not making a judgment one way or another. I just wanted to correct bitcoin2moron's inability to understand externalities and consequences of actions.
Personally, I'm of the belief that some porn does promote violence and/or a degrading outlook on women. However, that's only SOME porn. Definitely not all porn. It's something that needs to be taken on a case by case basis.