They can't make you do anything, you can always vote with your feet, but why not just solve it quietly without waves and rationalisations?
I have strong religious beliefs although I don't care about the 'queer' stuff as it's all irrelevant in my locale. I certainly would not be interested in attending a workshop about it. But I don't get into theological discussions with anyone, I would just quietly not attend. This is a common resolution in some cultures & locales. Something comes up at the last minute and they just quietly don't do it.
Then deal with anything about it afterwards when it's already a fait accompli, apologise and look faintly surprised if people start jumping up and down making a spectacle of themselves over it.