I get that he's a good man, but what's the basis saying he's a good man manager? Good managers, man and generally, make tough decisions, correct ones, and at the right times. RM seems not to do that. His team selections, and game management, often feel like he's trying to keep everyone happy, and can be baffling.
Also, I think that the players could give him more and some of his recent comments have alluded to that. Having your players give less than they should, and having to call that out publicly, alongside his selections etc, suggests to me that his actual management is not great.