I never understood why it's such a big deal. When people guess wrong about my gender, ethnicity, preferred spoken language, etc, I correct them.
I guess if they were to argue with me about the correction and insist their guess was right, that would get old fast and I'd be as frustrated as foone.
It happens much more frequently by people with malicious intent to them. All you have to do is say once that misgendering is annoying and them trolls will latch on and do it intentionally to harm you
