I've had one of those at one of the smaller MBB offices in Europe with an associate partner. It was extremely uncomfortable and I ultimately did not get an offer. I perceived him as very rude (he started the interview by semi-mocking my educational background). Example things the interviewer would say / do (it what was supposed to be an interviewer-led case):
- "I don't know, you tell me"
- "Really? [with raised eyebrows] And you're sure that's correct?" [in a condescending tone about something that was correct]
- If I asked a question and we were meant to explore a different issue, not providing any guidance about the next step whatsoever (so, treating it like it was purely candidate-led and just giving me dead ends)
- If I asked a clarifying question, he would give me an annoyed answer and basically tell me to hurry up
I had to muster all the self restraint I was capable of not to stop the interview, keep calm and barrel through. By the end, all I could think of was how rude this man was being to me. I actually work in consulting now and would never consider a job at this particular firm because of the impression he left on me. Do not want to work in a place that would hire people like that.
Bottom line: try to keep calm and answer the questions. But, if the experience was really bad, think about what that says about the kind of people at that firm :) The fact that you are an interviewer is not an excuse for being an asshole