If on the other hand he was just being his normal charming self, then I guess you now know why they're hiring. Nobody hires because it's awesome; they hire because they have to. Which is because the last person quit. Which is because of this asshole.
I've had rude interviewers, but never to the point of ranting like that. In the moment I mostly just keep going with the rest of the interview and make the best of it, but later on I always come up with lots of ballsy things I could've said. Including some version of the above like "OK I think I just found the source of your turnover problem" and point at the guy...