Why do you think that discrimination laws only apply in employment situations? Why do you think that the venue was going to employer her? It wasn't it was just hosting her as it does others.
You can't refuse a service for a protected characteristic. .
And who is going to be violent? Surely you are not suggesting that a lesbian KC is going to be violent? It's really not a good look for a venue to not be able to host an event on H&S grounds.
Is this the world you want to live in? One where women, lesbian women are refused an audience because some violent men think lesbians can have penises and want to shut up a middle age lesbian who says that this is lesbian erasure?
I hope that they have their asses sued off and if they state that they couldn't keep people safe and that comes out in evidence well at least it will show who are the violent ones and why.
And yes in the main hospitality staff are casual staff. If they refuse to work because they have bigoted beliefs what normally happens is that the venue doesn't require them again. They might try to bring a claim that they are being 'discriminated against' but they really are not, they are refusing to work due to a person's protected characteristic. They don't have to listen they just have to work. I mean try that on in any retail environment, refusing to serve for a protected characteristic. It won't wash. And any argument that the venue can't keep them safe should lead to the venue being closed for H&S grounds rather than being discriminatory.
In fact the staff who refuse to work can also be personally sued for discrimination should Joanna Cherry want to.
And as for Universities they should be expelling TRAs who are violent towards women. They should be the epicentres of free speech. As it is they are allowing women to be silenced in favour of males who are violent. If you think that this is acceptable in any way you clearly don't believe that free speech matters.
There are several threads on twitter where experienced barristers discuss this. The club and the staff are clearly in the wrong here.
https://twitter.com/RoddyQC/status/1653215267487461376