I get where you’re coming from, but I don’t think it’s the same thing. If someone says their name is Rachael and you say, well, that’s great, but I’m going to call you Sue because you look like a Sue to me, that’s disrespectful. We’re not talking about pronouncing tomato differently or something, we’re talking about people’s identities. By refusing to call someone “they” because you don’t feel like it or don’t believe in anything aside from male/female, you are squashing someone’s identity. No one is squashing your identity by asking you to call them by a certain pronoun.
I don’t accept the idea of telling people who are finally able to feel like themselves that they should ‘just get over’ people not respecting their wishes. That’s not being a decent human, it’s being kind of a dick, in my opinion.
The people who refuse to use “they” as a pronoun are largely doing it because they’re pushing back against the idea of the non-binary. Yes, they use grammar rules as a sort of excuse, but I don’t think that’s what it comes down to. I don’t believe people should have the right to ‘disagree with’ things like equality.