I thought of a lot of questions along those lines. My concern was that I didn't want to get too philosophical. A big part of the reason I don't want to challenge the nuts and bolts of these claims is that I already think that gender identity "education" lies well outside our mandate as a school and I don't want to send the message that we need to spend even more time discussing it. We should treat all students with dignity and respect, certainly, but this does not require us to believe what all of our students believe. Somehow this goes without saying in the case of religion - I am able to treat my Christian students with dignity and respect even though I do not believe that Jesus Christ was the son of God, and I've never had to attend workshop training that was geared at changing my religious beliefs - but not in the case of gender. So, yes, gender identity is incoherent as a concept and I'm sure they/them wouldn't have had a good answer to your question, but other than acting as a gotcha, this is rather beside the point. Similarly, I could, for instance, challenge their claims about puberty blockers, but again - we're not a medical institution, and I don't want to spend time discussing an issue that has nothing to do with our professional lives.