Well, the only thing that will really work is for people to stop employing/working with people who are abusive.
If a director exhibits abusive behavior, producers and theatres need to stop hiring him/her. If it's a producer, go get your financing elsewhere or decline to work with projects originating there.
My whole point here is that there are people that "everyone knows" are nightmares. But if there were consequences for their behavior (ie: work dries up), those people will either go away and be replaced by people who are, hopefully, not nightmares or they will change their behavior. Being abusive is not in any way a prerequisite for being talented or even being a genius. And continually making excuses and ignoring abusive behavior doesn't affect the genius, and will encourage the abuse.
The greater issue at the moment is retaliation. We need to figure out how to protect people who are brave enough to come forward and speak about their experiences with such people.