Bingo. Bisexuals are only marginalized when they are mistaken for homosexual.

What about being marginalized when you are mistaken for NOT EXISTING AT ALL?

Because that's the default, if you're bisexual. Sexual orientation is assumed to be monosexual by definition; thus, there's no such thing as bisexuality-- it's merely a fiction or delusion-- and therefore no such thing as bisexuals. So we must be either straight or gay. The former, if we're female; the latter, if we're male. We can come out till we're blue in the face, and it usually doesn't matter; we can't possibly be what we say we are. Because that's not real. WE'RE not real.

Think this just might pose a bit of a problem?

So the fact is, we're usually mistaken for gay, or straight. Because what else IS there? And that's just something we have to live with. Constantly being reminded that most people-- including GAY people-- regard us as something on the order of the Tooth Fairy. Only make believe.

That's what biphobia is, basically. And I think that it often flies under gay people's radar, because you're used to being on the alert for homophobia, and this operates somewhat differently. But (to mix my metaphors)... it's still poison.

We also suffer from homophobia, sometimes, of course. But while that's not the constant for us that it is for you... we get good ol' biphobia 24/7.