As an employer, I have found that if you honestly tell 10 people the reason that you did not hire them that a minimum of 3 people will have hostile reactions to you.

I do agree that it would be a better way for all employees to give feedback to all candidates and for those candidates to handle the rejection in an emotionally mature way.

Most companies do not handle candidate review in an emotionally mature or professional way, and the widespread lack of feedback is one of the ways they secure protection from possible downsides of their own blatantly disrespectful and sometimes outright discriminatory hiring practices.

Assuming that you are like the other 90% or so of employers who treat employees and candidates exceptionally poorly (I'm not saying you are, just assuming for a second), then getting only a 30% rate of feedback calling you out on use of superficial, inconsistent, and (in some cases) borderline (or even blatantly) illegal reasons for rejecting a candidate doesn't sound so bad.

It suggests to me that candidates on the whole are more professional than companies, but companies can use certain bureaucratic policies and processes to make sure they effectively hide the unprofessionalism from ways in which it could come back to negatively affect them.

I'm sure it's not for no reason. Is it difficult to imagine a (particularly bad) candidate throwing a miniature temper tantrum if s/he knew that leaving before lunch was a rejection?

> candidate throwing a miniature temper tantrum

This happens?

In my previous company, one candidate became belligerent and physically pushed interviewer away from whiteboard after interviewer told him that his solution is not correct. Interviewer asked candidate to wait a few minutes, left room, called recruiter who in turn called security to escort candidate out. My desk was just outside interviewing room and I saw the long glance that the guy gave to interviewer - it was "if i see you again, I will kill you". Or at least I interpreted it that way.

Company (and interviewer) decided not to bring charges so I assume he continues to interview at other places. There are non-zero number of unstable individuals who do not handle rejections or criticism well.

And the problem here is that there is no recourse for the company to help stop this individual from being the same problem for somebody else.

Sure beats finding out after you hire the psychopath.