It's inexplicable. I think it's just a case of being overly defensive with little understanding of gay issues. Especially with that reaction to your suggestion of bi in denial (which I agree with); you were in no way claiming that bisexuality should be some "ugly, dirty secret", but it doesn't erase the fact that some bisexual and even homosexual people can be in denial for various reasons. Also, some bi and homosexual people may actually feel that their sexuality is an "ugly, dirty secret", but that's something we should work towards fixing, not project onto others and then get offended. I wholeheartedly agree with your point on words needing meaning and being defined collectively.

I think we all need to be able to recognize and call out the bad actors/transgressors within and from our own communities or at least not jump on others who do, because we understand the nuanced issues at stake.

Exactly. Bisexuals do that less than other groups, which is causing bis-in-denial to wreak havoc on everyone's understanding of sexual orientation. I just think that because most bi people can blend into another group, they just feel they don't have a dog in that race, but yet they still feel personally attacked when the fact that these people are bi is mentioned.