I've got a girl who I might be dating soon that's clearly a TRA and has a non-binary friend. She thankfully doesn't bring up trans or NB shit, but I'm worried about what I'll have to do when, not if, she brings up those topics. We've already had the JK Rowling conversation on our first date, and I said that while what she said might have been wrong (even though it was perfectly reasonable), she, like everyone else, is allowed to have her own opinion and if people don't like it, they can put their money where their mouth is and not buy her books or merch, rather than threaten her online; we quickly stopped talking about it and she hasn't brought it up since.

In regards to your boyfriend, you need to see if he agrees to disagree. If he continues to doggedly pursue this ideology, and force you to support it too, it might mean he doesn't care about your own thoughts and feelings, even though you clearly respect his right as a person to have his own. At no point in that conversation did you insist that he changes, and yet he kept implying you're a homophobe (even though that has nothing to do with NB) and a transphobe (which again by their own lack of logic shouldn't include NB either since they're not transpeople, they're not part of the gender binary, so to speak).