You know, I had no idea how much raw biphobia existed out there until something like 3 years ago when a huge fight broke out in a very large Facebook LGBTQ group that I help moderate. Somebody made a post about how she would never date a woman who had dated men — that any woman who would date a man could not be trusted by lesbians.
I deleted that post on the grounds that it was contrary to our group guidelines of being respectful of all LGBTQ people, that the B stands for bisexual, and that bisexual people should feel as supported in the group as lesbians.
I really didn't expect pushback, but I was quite mistaken. I was inundated with messages from lesbians telling me I was wrong, that they are perfectly free to dislike and mistrust bisexual women, and that they should be perfectly free to express themselves.
I was shocked.
I don't want to give the impression that most of the lesbians in the group felt that way; quite to the contrar, actually. But a loud fringe certainly made their biphobia as public as they could make it.
Some of them ended up leaving the group over not being permitted to share biphobic posts.
So I can only imagine the pushback that novels might might receive over bisexual characters.
I guess the only real solution, as you say, is to keep writing. So, please, keep writing!