Yes, I think the boy answered rudely. But I think not getting an immediate reply and then forcing the issue wasn't the best plan for getting a polite reply. It was *in my opinion* a set up for the rudeness. Not that it excuses his rude reply.
The boy is a guest, and no matter how much you don't like someone else's parenting, you mustn't take it out on their kids. If the boy didn't give an immediate reply, probably best to let it go in the heat of the moment. Later, when the mood is changed you can talk about how "in our house we do it this way."
If the boy and the host have an issue between them that puts the host in a position where she feels ill will towards him, then perhaps she should reconsider hosting him. I know I have feelings about one or two potential guests that preclude me from inviting them without their parents. Do you know what I mean?