There comes a time when in every community you have to do something you don't like. Maybe it's a task that no one enjoys doing that has to be done for a release. Or maybe it's the difficult task of talking to someone else and telling them to stop.
When looking at open source and focusing on transparency it is crucial to handle every situation with grace and tact. Just because you're open, transparent, and honest, does not mean you need to be rude. You can still be open and honest and polite. But you must communicate. This is important when you have to redirect someone; or tell them to stop.
Keep in mind they may not even realize the detrimental effect they have on those around them. And you must communicate with them the greater good. Sometimes the best thing a volunteer can do for their community is to step down. Maybe they're burned out but they don't realize it or they exhibit the symptoms in a different way. They may take out their frustrations on other volunteers, they may throw up a defense for every decision they make. Whatever the symptoms might be if the root cause is burn out they need to take some time off. And you must help them to realize that and see the importance of it.
I'm not saying it's an easy conversation to have; I'm not even saying they're going to listen to you when you talk to them but your job is to talk to them. In open-source community where everyone is equal it becomes critically important that these conversations are held and that people communicate effectively. Without this transparent communication people will remain in a situation where they're not happy and may not even realize that they are unhappy ... or worse block others from contributing and volunteering.