i don't necessarily think it's fair to jump to "they hate polyamory and are using intentionally harsh language to signal a desire for its destruction" when you could also just like, assume the person was speaking very casually

sometimes people jokingly refer to a thing in a semi-derogatory manner even when they approve of it or are a part of the in-group in question. for instance i'm trans but i regularly say stuff that i would find highly suspect in your average cis person, but probably not your average leftist (at least here).