If we take the interviewee's story as truthful, then it sounds like a lot of the interviewers in the room could bear to learn the same lesson here - don't belittle candidates because you never know when or where you'll see them again.
It's too vague to be helpful. For example, the "dogmatic principles" criticism. The interviewers could have asked "Is security a good thing?", and he could have answered "No". Or the interviewers could have asked a silly question like "Tabs or spaces?" and berated him for answer answering "Spaces". Context is absolutely important.
And if we take the story as truthful, he just went up and said he's done with the interview, without explaining the reason to the room. He pretty clearly didn't explain to the room that he did not feel that he was a good fit, and did not want to further waste anyone's time. That's the only logical explanation for why the lead had to track him down in the elevator, to understand why the interviewee decided to end it.
I am pretty sure, that the candidate would get no detailed reasoning why he was rejected if he were get no offer.
Why do you think he owes explanation?
