Most of us are familiar with the police interrogation technique of "good cop, bad cop." The "bad cop" berates the suspect and asks tough questions. The "good cop" is friendlier and offers a better deal or at least some respite from the "bad cop."
There are times when committees need a bad cop. I'm not talking about a devil's advocate who points out the flaws in a proposed course of action. I mean a person who is willing to say what no one else is saying about not just a proposal, but the group itself, its history, its conflicts, and - to use an overused term - its hidden agenda.
Whereas the devil's advocate role in a group should be rotated around so one person doesn't get stuck with that responsibility, I've found that the bad cop role has less mobility. The reason is the bad cop says truths that are so hard to take that the role can only be assumed by someone who is beyond ambition; an ultra-senior person or one who doesn't have an eye on advancement. This is a person who doesn't care if the china gets broken just so what needs to be said is said.
Bad cops are rare on committees and boards. They have the capacity to irritate everyone - even those who agree with them - and few people have the requisite personality. There are times, however, when the bad cop glitters and sparkles and, although never thanked, saves an organization.