These things come down so much to a particular interviewer. I recall hearing about one situation where a person who was interviewing for medical school was "attacked" by the interviewer to the point where she was in tears by the end of it. She was an incredible candidate. It's a great school. She is not a person who breaks down easily. This one interviewer was just a complete ass. What do you do? If it were me, I think I would say something polite to the fact that maybe this isn't the place for me, thank him for his time and yes I would walk out. I actually got really angry when she told me about it. There is simply no excuse for an interviewer to act that way.