I'll go one further. "The nasty one" is a role that usually begs to be filled, even in a good cause. Sometimes it's even essential to progress. "Good cop, bad cop" works. I'm more likely to play "bad cop" myself, though at least I'm usually aware of it being a situational role. I've definitely said things that would have violated a CoC if there had been one in those situations, so I do understand the fear of them, but here's why I chose that particular metaphor: even the bad cop is usually working within limits. That dynamic can still exist, and still be effective, even within the limits of a CoC. People can still be demanding, critical, even abrasive ... and they will. They just can't be bigots or harassers and expect to keep getting away with it.