I agree with "prejudiced against polyamory." It emphasizes prejudice, i.e. making a total judgement against someone based on one specific feature, rather than considering their entire personhood.
If you really need a specific word (can't imagine why), I propose "amorist." Racist, sexist, ageist... At first, I was thinking "polyist" but then I realized none of those "ists" suggest being against a specific race, sex, or age group - only against "other" race, sex, or age groups.
Originally Posted by Tonberry
I've actually seen "polyphobic" a lot. Didn't realise it had another meaning.
I don't think we need a word for any kind of discrimination or prejudice. We can just tell someone they're prejudiced or bigoted.
Hmm.. except "heteronormative" just means you fit succinctly in the heterosexual box. It doesn't imply that you have anything against homosexuality. So by analogy, mononormative just means you're naturally inclined towards monogamy, not that you necessarily have anything against polyamory.