What is the status of a Muslim who says homosexuality is genetic?

Actually that’s an opinion, where they may have no medical proof. One may have a personal inclination towards it, but the point is simply because one has an inclination does not justify its application. Simply because you have this feeling, doesn’t mean that you are justified doing it. It’s not established scientifically and it is not correct in fact.

If some genetic link is found, even then it would remain haraam and forbidden. By simply saying that it is genetic one doesn’t become kaafir; it is a scientific opinion.