>in practice the people who say it are motivated by a package of ideas about gender which I think are bad and would be harmful for society if they were more broadly adopted
I would argue this is a symptom of the same phenomenon and therefore the heart of the objection is still the same.
Is it possible in your view for any new trend to be bad and worth fighting against? It's hard for me to see how this doesn't reduce to a content-free "nothing really matters" objection.
Sure, if there is any evidence behind the objection I can support it. When the objection is some vague claim about it being "harmful for society" without anything to back that up, I will call BS.
I would argue this is a symptom of the same phenomenon and therefore the heart of the objection is still the same.