Monoromantic

Monoromantic refers to someone who is romantically attracted to a single gender. Monoromantic refers both to gay people and straight people and is typically used by multi-specs to refer to anyone who is not m-spec (multiple gender attraction spectrum) (with the exception of a-specs, who are attracted to zero genders). It is similar to the terms cisgender or alloromantic in that way. It is commonly used when talking about monosexism; the prejudice against biromantics and other m-spec identities.

The sexual counterpart to monoromantic is monosexual.

Monosexism
Monosexism is the belief that monoromanticism (either exclusive heterosexuality and/or homosexuality) is superior to or more legitimate than multisexuality.

Homophobes see non-monoromanticism as morally wrong, as sinful, dangerous, or deviant. Some gay people dismiss bisexuals as lacking in self-acceptance, and claim that m-specs are actually gay but are in denial. Others see see m-specs as trying to maintaining straight privilege while simultaneously trying to get into LGBT spaces.

Another common attitudes toward bisexuality, especially among heterosexual people, is the fear that their m-spec partner will leave them for a member of the same sex. Similar fears exist among gay people as well, leading to the stereotype that m-specs are more likely to cheat. There is a belief that multi-specs will eventually get married and "choose a side", dismissing the fact that multiromantics are still attracted to multiple genders after they are married.