> they would have to rebuild their entire worldview around gender

I don't really understand this. When I'm talking to an adopted child, I have no trouble calling their parents their parents, even though they're objectively guardians. When I'm dining with religious folks, I have no trouble saying "Amen" or some such phrase from their religion despite me being an atheist.

Saying something you don't objectively believe out of consideration for others' feelings is normal, and it's fairly basic manners.