I feel you on the biphobia you've experienced, and I'm sad to say I've participated in that kind of erasure for myself because the bisexual identity is one that has left me unsatisfied on a personal level, hence taking on both "lesbian" and "queer" which all together have enabled me to speak more coherently about my sexuality.

The idea that bisexuals aren't sexual minorities is such a terrible, and yes, ongoing myth and needs to keep being busted.

There's a lot of biphobia in my locale from the LG community and a lot of erasure from the more radical queer community and my own community activism (such as it is) does attempt to combat that - identity politics are a finicky thing.