The one person I know IRL who is extremely militant about it was an old teacher from uni. Since her son came out as trans she hasn't shut up about it and tbh I never had an issue with the whole trans thing until she opened my eyes to the dark side of it.
Also I was part of a women's conference in my industry recently and one of the main stage speakers (it was all virtual) was a non-binary person (obvious biological woman but presented very masculine) and they were the rudest, most obnoxious person I've come across in a long time. They stumbled into the call about half an hour late, completely interupting the woman who was in the middle of speaking and started yelling if people can hear them. Then they introduced themselves by declaring "I am non-binary!! I do not identify as a woman!! I have both masculine and feminine traits and if that offends you too bad!!" ...as if not everyone on the planet has both masculine and feminine traits??!

They also said they were at a restaurant and was eating into the camera the whole time, people starting complaining that the background noise was drowning out the other speakers. Awful, awful person.
I think there's a portion of MtF and FtM trans people who even think non-binary people are full of
tit lol