Oppression of bisexual people is based in part on heterosexism and in part on monosexism, the belief that people can or should be attracted to only one sex/gender and that there is something wrong with those who cannot or will not choose.
Source: wiktionary
Considering the fact that the overwhelming majority of biphobia and monosexism originates not from gay and lesbian communities but from heterosexual structures, […]
Source: wiktionary
[…] The L Word seemed to harbor its own reservations about Alice's bisexuality from the start. But that the show ultimately chose to project its own monosexism through the voice of the one character who initially defied such limitations set a new record for implausible character noncontinuity, at the same time as it closed down one of American television's most prominent discourses on bisexuality.
Source: wiktionary