Due to the nature of the typical personalities that tend to gravitate towards stage management, I find that quitting jobs isn't discussed without some trepidation, whereas if someone was in the same toxic environment in the corporate world, they may have quit sooner and been proud of it. I think it's our nature to stick it out for as long as possible because of the small world we work in.
I think part of the problem is a producer-centric world where stage managers may often be asked to perform above and beyond the call of duty, with little support, and times little pay - and continue the mentality that if you quit "You will never work in this town again!" - regardless of how toxic the work environment is.
Silly, huh? Maybe if more people quit these terrible jobs, producers would understand the cause of the toxic environment is not bad stage managers, but the other causes.
I think some of it is ingrained in us through our training and experiences, We are told to put up with tough personalities, deal with people yelling at you for things that aren't your fault, work for low pay at really inconvenient times, travel away from friends and family, start from the ground floor and work your way up, put in the hours that are necessary to complete the work (which for us means to make it perfect) which is never just 40 hours.
We are never told what "isn't" our job, when it is too much, when you should say no, when the experience that was great for someone else might not necessarily work for you. That's the stuff I fear everyone learns the hard way.