Like "sexist" or "racist," but in reference to being gay?

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,[9] sexual prejudice, anti-gay bigotry, straight privilege, The Straight Mind (a collection of essays by French writer Monique Wittig), heterosexual bias, compulsory heterosexuality[10] 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.