It's sort of obvious, but it was still wrong for the host to do that when Tim Cook has never publicly acknowledged his sexuality.
I don't think that's fair. Cook has never hidden the fact that he's gay, he just doesn't talk about it himself, and it's his right to not to do so. I'm pretty sure he's not offended by people knowing or talking about it, although he'll probably continue to refuse to talk about it, because he doesn't have to.
Cook isn't in the closet, so it's odd to talk about him being outed.