I think the general tone about not putting up with abuse is good about this - finding your line, what acceptable level of "bad behavior" you will put is part of your style. And it's great that this business is changing what is acceptable behavior, but until everyone learns new rules, there will always be a place for stage managers who have the thickest skin and can put up with the worse of the worse form actors and stage managers. (There will always be difficult, demanding actors, directors and designers - and a place for SMs who can work with them.)
Again, I don't think the actress is unstable, nor insane - and I think that perhaps very few people are taking a moment to see it from the actor's point of view. The SM is a replacement stage manager (she probably is the one who knows the show the least, other then the new actors they are putting into the show). The evening of the event the composer/musical director/possible producer did sort keep going over rehearsal time, and then sort of slammed the non-equity actors by asking them to stay late (not the best atmosphere - and how many thing this was the first time). We also assume the SM was not at the fault of this - the SM may be coming across as speaking down to them (I see this all the time). At the end of the day, this is sort of a SM Said/Actor Said situation. I would love to get the actress side of the story, especially before we call her insane.
And you can apologize, with out telling someone it is your fault. "I am sorry you feel this way." "I am sorry this situation has gotten out of control." "I am sorry, I never saw the situation from the point of view." "I am sorry that this has gotten you so angry. Can we discuss this tomorrow? Later tonight? Over drinks?" You have to learn how to diffuse these tense situations - with yelling or without yelling. I have dealt with a lot of actors talking them down form quitting a show because they don't like A, B or C.
The SM in question handled it well, although I think walking away is often NOT the best thing to do - it sends off all the wrong non-verbal communication. (And if indeed she is unstable or insane, who wants to turn their back on the insane ;-) )
Again, I think there is perhaps an age and gender angle to this situation - where I feel like as a middle aged man, I can take childish people yelling at me and sort of shrug it off - it's amazing how often I get complimented on how I don't let it get to me and how I don't get sucked up into it - and how I actually I seem more in control of a situation by just letting it bounce off me.
But again, that is my personal style.
I am getting worked up because it seems like no one is stopping to see it form RB's point of view - which I think is important.