This is very unconventional. I'm honestly not sure what they were thinking--interviews are supposed to be private. I imagine you weren't the only one who wanted to get the hell out of there. I would be offended if a potential employer pulled that on me. I would have considered walking out. And depending on (a) how much i needed the job or (b) the likelihood of getting a second, private interview, contemplation would precede action. and out the door I'd go. I'm sorry they did that to you. At the very least they should have told you in advance to mentally prepare yourself (and the other applicants as well).