As an interview question, "What's your favourite language?" is only interesting if you don't ask it having a "correct answer" in mind.
Depending on when you learn that you have to leave, you can either say "Sorry, I won't be able to stay for the whole duration of the interview" or "Sorry, I'm needed elsewhere, my colleague will handle the rest of the interview". Leaving without saying a thing (even if it's just a nod and a smile) is more disruptive for the candidate than saying nothing.
That is true, it's not the nicest way to leave, certainly not how I would. But we all know "no nonsense" people who behave this way. All I'm trying to say is there's no definite reason as to why he got up and left.
I really dislike how you commiserate over this post like he's some sort of victim.
OP should humble himself because A. It's not really that big of a deal, it's an opinion....about a dead language B. it's kind of an expected response in this industry. He also says himself that he doesn't even know if he asked what his favorite language was.
It doesn't really matter why - I don't see any excuses for rude to someone in an interview - particularly someone who has just supplied a perfectly reasonable answer.
Depending on when you learn that you have to leave, you can either say "Sorry, I won't be able to stay for the whole duration of the interview" or "Sorry, I'm needed elsewhere, my colleague will handle the rest of the interview". Leaving without saying a thing (even if it's just a nod and a smile) is more disruptive for the candidate than saying nothing.