heterosexism might be what you are looking for.
According to M-W:
: discrimination or prejudice by heterosexuals against homosexuals
This idea is expanded in the wiki article under the same name that states:
Heterosexism is a system of attitudes, bias, and discrimination in favor of opposite-sex sexuality and relationships. It can include the presumption that other people are heterosexual or that opposite-sex attractions and relationships are the only norm and therefore superior.
Interestingly (also on the wiki page - I highlighted the single-word terms):
Given this lack of semantic transparency, researchers, outreach workers, critical theorists and LGBT activists have proposed and use terms such as institutionalized homophobia, state(-sponsored) homophobia, sexual prejudice, anti-gay bigotry, straight privilege, The Straight Mind (a collection of essays by French writer Monique Wittig), heterosexual bias, compulsory heterosexuality or the much lesser known terms heterocentrism, homonegativity, and from gender theory and queer theory, heteronormativity. However, not all of these descriptors are synonymous to heterosexism.