I say “the experts”, there’s only one person cited here but still. I saw this floating around tumblr today and thought it was worth sharing.
“A primary manifestation of biphobia is the denial of the very existence of bisexual people, attributable to the fact that many cultures think in binary categories, with each category having its mutually exclusive opposite. This is powerfully evident in the areas of sex and gender. Male and female, and heterosexuality and homosexuality are seen as “opposite categories.” Those whose sexual orientation defies simple labeling or those whose sex or gender is ambiguous may make us profoundly uncomfortable. Thus, bisexuals create discomfort and anxiety in others simply by the fact of our existence. We are pressured to remain silent, as our silence allows the dominant culture to exaggerate the differences between heterosexual and homosexual and to ignore the fact that human sexuality exists on a continuum. It is much less threatening to the dominant heterosexual culture to perpetuate the illusion that homosexuals are “that category, way over there,” very different from heterosexuals. If “they” are extremely different, heterosexuals do not have to confront the possibility of acknowledging same-sex attractions within themselves and possibly becoming “like them.” There is considerable anxiety in being forced to acknowledge that the “other” is not as different from you as you would like to pretend.”
–Robyn Ochs: Biphobia