But this is like drugs ain't it? People will say drugs should stay illegal otherwise it encourages use. Besides the fact it's not true, the simple reality is drugs exist whether people like it or not. Best thing we can do is limit the criminal element.
Sex has an even stronger argument along those lines as I'm sure you'll agree. On a primal level it's the most basic thing we desire. Plenty of people are into kinky shit you probably disapprove of. But you said yourself, every man and woman has their own moral code. So why should others be judged by yours?
Best way to avoid actual harm coming to people in these things is to have it as regulated and legitimate as possible, because either way people are gonna be into kinky shit and will wanna watch kinky porn as a result.
I think the way Kink.com does it sets a good example. You watch their videos and they do interviews with the performers before and after. You know they have safe words etc. They should all be like that ideally. If there was more regulation they would be, and if there was less stigma from people like you, the women in that industry would be more likely to speak up when abuse does occur (I mean actual abuse here, not just sex acts your gran disapproves of).