If the guy is a disaster as a human being, then he usually can't be a very good coach, even if he knows a lot about baseball. A coach needs to know how to deal with his players...it's a major part of the job description.
I had a coach when I was in my early teens who, it later was revealed, was a child molester. Sorry...i don't give a damn how much BB he knows. I know of another guy who constantly screams at players using profane, mocking and abusive language...again, sorry, I don't care how BB he knows. He's the sort of guy that would make my 16yo quit BB.
I have no problem with a coach who calls players out for poor play and behavior, as long as he is fair. I actually like some of that. There are a few too many coaches around here who don't enforce discipline, i.e. threaten to bench players but don't, and the team morale as a whole suffers in the long term.
Having said all that, the best BB coach I ever had was soft spoken. He seldom raised his voice. He would bench you if you didn't listen though, and move you out of key positions(SS. P, C, batting order)if you couldn't do the job.