Very good points. There are many parallels here to what happens even inside the LBGTQ community where tolerance is supposed to be a lesson hard learned by everyone in it.
For example, if a lesbian doesn't want to date a bi woman because she can't stand the thought of her gf having been with a cishet man, all she has to do is not go for those bi women. She doesn't have to like it or be enthusiastic about heterosexual intercourse. But if she goes around saying bi girls are gross and that only 'gold star' lesbians are really lesbians deserving of their own spaces (bi girls are invading lesbian spaces), well, she's going to have a harder time of it. She'll probably be thought of as a 'radfem' or a TERF, and fewer people will invite her to the True Agenda SettingTM parties.
However, there will be some people who, even if all she does is say she's not into bi girls, will still call her a TERF, even though that's not an idea that is accurately grouped in TERF ideas. That's wrong to do too.
Why is it necessary to apply the slur 'TERF' to anyone? How is it different to calling gay people 'poofs'?
What are 'TERF ideas'?