I really don’t like how Stephen wrote him off with a joke at the end though. Stephen seems like a smart guy, but it seemed a bit condescending here.
When Stephen asked about something coming from nothing the obvious retort would be to question where God came from. If God is allowed to exist without a prior creator then why can’t the universe? Attributing creation to a god doesn’t get round the issue of something having to have either come from nothing or to have just always been. All it does is change the prime mover from being the universe itself – or some prior physical process – to it being a supernatural entity.