Bifobia

The association of bisexuality with promiscuity stems from a variety of negative stereotypes targeting bisexuals as mentally or socially unstable people for whom sexual relations only with men, only with women, or only with one person at a time is not enough. These stereotypes may result from cultural assumptions that "men and women are so different that desire for one is an entirely different beast from desire for the other" ("a defining feature of heterosexism"), and that "verbalizing a sexual desire inevitably leads to attempts to satisfy that desire."