Just a feeling. I have no proof.
And, It should go without saying, respecting one's identity is the least we can do, including the gender since it's in there. Except, of course, for horrible stuff, but surely gender is no such thing.
Actually, while I don't care about my gender, if you are not ready to respect my fellow human beings and their identity, I don't really want to have to interact with you.
When you say "not caring", do you mean "Can't be bothered to use pronouns people wish to be referred to" or "don't mind being called with whatever pronoun?" Because the phrasing is ambiguous and two of the possible meanings are radically different things.
At this point im not sure if socially constructing your identity is that common outside of your teenage years.
then I'm with you, a part of the problem is there.
Actually this doesn't match your first sentence, trans people pretty much care about their gender. I believe only a part of the non conforming people don't care about their gender.
Anecdote but as a cis male not caring about his gender, I never quite felt hostility against me in particular (against the male gender, sure, but I understand this hostility)
I'm confused by your comments so I'm trying to clarify by making things more explicit.
To me, "non-conforming" here means LGBTQIA+. "cis" is the closest thing to "conforming". "trans" is pretty much "non-conforming". I suspect we are not agreeing on this. What do you mean by "they" and "non-conforming"? If we don't agree on those words, it most likely follows that I don't agree with your following sentence "This results in the discrimination you speak of."
This is very abstract. An practical example: Answering "How would i know?" to "What are your pronouns?" will get you this kind of covert hostility.