It wasn't without warning, it's been said that it was on advertising or promo material, plus if you booked to see him then presumably you know who he is and what happens in his shows.
WRT the last bit you have written, I may have missed something salient, but I have never seen anyone on here supporting a rapist or far right politician or racism, just because it's "anti-trans". Also most GC people that I know, follow online, or recognise on here aren't "anti-trans" as you call it, but just are pro women and children, and don't agree with young people being given damaging drugs to fulfil an agenda promoted by the likes of Stonewall, Mermaids et al.
Like I said though, I may have missed something so if you have evidence of people supporting rapists just cause they're anti-trans, please share as I find that abhorrent and would like to know to steer clear of those people.