I agree with the "don't give them feedback" but for a different reason. If the company has this psycho in there interview rotation, he sends a strong negative

I agree with the "don't give them feedback" but for a different reason. If the company has this psycho in there interview rotation, he sends a strong negative signal, basically the company has a "tell" that candidates can use to avoid this guy or companies that would employ him. If the recruiter coaches them to hide their "tell" [removed the guy from the interview rotation], they haven't really fixed the problem, just hidden it. Now, the next guy/girl who interviews won't know about the horrible guy he/she will be working with because the company "hid" him from view until it was too late.