My friend tried to come out as polyam to faer partner but he told fae that you can't BE polyamorous. He said you can like the idea of a polyam relationship and be in a polyam relationship but that it isn't an identity. How can fae explain that it is an identity and that it is a part of who fae is? Fae is reasonably hurt by what he said and I want to help to the best of my ability.
Is your friend’s partner a reader of Dan Savage, perchance? He likes to bang this drum - that polyamory is something you do, not something you are. It’s a common argument, but one I don’t subscribe to. You can see my FAQ page on this question here.
I am sorry you hear that your friend got a negative reaction from faer partner, but there’s not much you can do to change that. He is going to say, and believe, things that you as a third party can’t change or control. You can point your friend to these resources; if you’re close with the partner you can try to share them with him as well. And you can help your friend process these feelings of hurt, guiding and advising fae as best as you can as faer friend. Be there as a listening ear, honor and respect faer identities, and help them recognize when a partner’s behavior is unacceptable.