@Violet869
This is a UK site - I left the UK some while back so I accept that I may have missed some nuance.
Yes I do think that posters were highly judgemental! Of him. They were saying that he thought she was a sex worker, not that she was one. Tbh, it's a pretty ridiculous conclusion to draw for all sorts of reasons. But that aside, if he drew that conclusion, I simply don't see how that reflects badly on her. It reflects more directly on his poor judgement in thinking this was a commercial transaction rather than a bit of fun (and the fact that he is someone who is OK with using sex workers).
And you make nothing of the claims that he was doing it as some sort of fetish. That's really very clearly critical of him. The word 'slag' wasn't mentioned. I just searched the entire thread using ctrl-F.
In contrast, there were loads of comments that were highly uncomplimentary of him. Here are some: "his shitty way of telling you that last night was not the start of a beautiful relationship", "He’s a shit. Stay clear", "He’s a nasty misogynistic piece of work", "Post him a picture of you donating it to a charity to support sex education for average men", "I'd block him without so much as a word", "It's just insulting. Block him. Dickhead.", "He’s a twat. Please do text him. Men need to be called out on shit like this". "Ignore, this is sounding a little PUA in some ways". I could continue. This is just from the first few posts, and more than was uncomplimentary of the OP in the entire thread.
There's no judgement from me btw. Casual sex isn't for me - it would fuck with my head - but I envy those of a stronger disposition.