Not at all.
They didn't just "go out" on a normal night out.
They were specifically told it was a men only do, and that they had to wear skimpy dresses and matching underwear. If I was told that, I would turn the job down, because I'd have a very good idea of what sort of evening it would be.
Opting in to wearing a certain outfit is not tacit acceptance that you will be sexually assaulted. I mean, even in a strip joint where the girls are wearing no clothes groping is strictly unacceptable.