I keep dating homophobic bisexuals (and it makes me sad :( )

This post is about bisexual folks who have homophobic friends and keep making excuses for them and end up choosing their homophobic friends over their gay partner/friend.

I'm so scared to talk to anyone about this, which is why I'm doing it pretty much anonymously. I'm so scared of being labeled biphobic, but, this is the third time this has happened and I have no idea how to move forward in my dating life. My bisexual partner of 4 years and I just broke up, my ex's community was homophobic, in a very subtle way that was hard to explain or pinpoint when I was in the midst of it, to the point where my partner was telling me the community was a great space and all the cis het white men there were "super woke", and if I couldn't make friends in that space it was because I wasn't trying hard enough, and why couldn't I just be friends with all these amazing people!?!! I internalized a lot of that, and my self-esteem went down the toilet for over a year until we finally broke up a few months ago. Then recently someone from the community realized what they were doing and they were like, "Woah, this thing we're doing and the way we structure our community and values results in really shitty experiences for gay and lesbian people (and older folks, and black folks, and monogamous people) people in the space." And I read this person's post and it all clicked! We had a lengthy conversation, and I then brought all of this up to my ex, who told me "Yes, my community struggles to undo its heteronormative and racist power structures," as in, my ex finally recognized these issues, and admitted that the community is still having homophobic and racist issues, but still chooses to to stay. They choose their homophobic friends over their gay partner. I also had a very similar experience in college with a friend, when my very best friend at the time started dating a homophobic man, and just cut all contact with me overnight because her new boyfriend was uncomfortable with her being friends with a lesbian.

Obviously these are shitty people and my life is better without them in it, but I have no idea how to avoid these kind of situations again. I feel like I have a really good read on someone, and then it just happens seemingly out of the blue. I have no idea how to avoid this going forward. The only way that feels like it'll fully protect me from this shit again is to just not date bisexual people. When my ex and I met they were so kind and friendly, they were on an LGBT committee where they were actively changing the rules at their women's college so that trans women could attend, and most of their friends were LGBT. And then two years ago, they graduated and we moved and they got this new group of friends that are mostly straight and cis, and are incredibly exclusionary towards gay folks, most of them basically just will not be friends with gay people, but because they don't say that outright, and they were super friendly to my bisexual partner (who sometimes refers to themself as gay, in an umbrella term way) my ex just wouldn't believe that it was happening, and would defend their friends and community over me every single time.

I guess I'm looking for advice, and a place to vent. . . And maybe connect with other people who have experienced this?