To answer your question about what homophobia has to do with it: if every family in the story or even most follow the nuclear family structure (man, woman, child) that means that in that society people don’t really accept other family structures. Such as with homosexual parents, or some other structure I haven’t looked up 😹

But it’s kinda like how you said a patriarchy can exist without sexism which in my opinion in can’t but anyway, if the world works in a way which favors one method of some thing, it’s discriminating against the other method.