TL;DR: grownups tried to bully all the "not normal" kids in one go, forever. They're lucky this push-back is so civil. Here's a take on why this theme looks familiar: it's patriarchy.
When you have negative politicized action to reinforce "traditional" gender roles, it's always in defense of a hierarchy, with hetero men on top ("patriarchy")*. Embracing equality pushes the social norm towards treating people like people, regardless of gender, eradicating the social barriers and roles in that hierarchy. This effectively tears down a whole kind of class stratification and the power structure that comes from it. It doesn't scare people; it directly threatens their power and feels like a personal attack, which fuels all the moral licensing needed to be deviously underhanded in retaliation.
IMO, we should quit being surprised and outraged, and instead just expect that some knuckle-draggers are going to show up to try and ruin a good thing. Because as long as someone is invested in punching down on others, it's possible that they'll punch all the way to some position of authority if nobody stops them.
(* I have yet to witness a conservative regressive matriarchy, but I'm sure they exist somewhere.)