Ok, look, you say 'something potentially nasty', right?
Then you talk about 'a woman who decides to engage in a commercial transaction that she feels safe with'.
Sure, those two things are not the same - but only because you've only focussed on one side of the issue. Which is precisely what I have the problem with.
Yes, if you ignore the women who are not feeling safe, then prostitution may well seem fine. Just as my other examples feel fine for someone who feels safe and happy.
But the point is that the experience of the person who feels safe and happy doesn't really help the person who feels upset, threatened, or abused, does it? The person who gets a warm glow from being cat-called, and who insists on telling the person who feels threatened and upset by it about that, is only being smug and insensitive. They're not cancelling each other out.
I do think that supporting one kind of prostitution supports all kinds. Sorry, but I do. We do not currently have an extensive system for making sure prostituted women are safe and healthy and happy, do we? So there is no possible way anyone can currently be confident they're with someone who is happy with what is going on, let alone consenting.
It's not like you're going to find a woman who says 'shit, I've just been trafficked across from Romania, someone has threatened my children if I don't pretend to be consenting and happy, but, hey, I'll spill my honest-truth story to the nearest punter', are you?
I'm not trying to be sarcastic with that (I know I come across as sarcastic sometimes when I'm not) - but I do think it's the basic important point.
All that happens when someone promotes one niche area of prostitution as safe or valuable or pleasant, is that unscrupulous people will make their brand of abuse look as much like that as possible, and people who don't care to enquire too much will happily give up their minor qualms and go ahead with abusing women.