Statistically, it lowers the number of rapes, because the pervert who would have committed one has porn to act out his fantasies. I think that alone would say that porn does serve a good purpose.
Also though, the women aren't forced to do what they do. They're offered payment and if they deem it "worth it", they do it. Simple as that. I don't necessarily agree with things like bestiality, incest, etc.. but going back to the rapists, they need porn to act out their fantasies.. and usually these type of porns are fake (well not bestiality obviously) in the first place, with just the pretense that it's incest or whatever.
So overall I'd say porn has it's place in society.