For me it was teaching as an adjunct at small colleges and universities over the years. The competitive dynamic made me literally sick for a couple of reasons. First, the initial power imbalance is quite extreme when you have people with the same qualifications working in an environment where some are full-time with benefits and good pay and others are working at the poverty line with no benefits. This creates a subconscious drive in those with the power to keep the disimpowered faculty demoralized. It is like backwards reasoning - the people with the pay and power need to keep that position, so the equally qualified individuals w/o pay need to be kept under their heels psychologically. I don't think there is any hope of a healthy dynamic when the structure is so out of balance.
This results in the faculty in power to compete with the disempowered over the most trivial, image based details. The adjuncts are just trying to figure out how to get enough money to cover the bills. You are functioning at a survival level reasoning, so when you are put down because someone is protecting their own image, it goes beyond insulting. People are playing two completely different "games". One is trying to survive, the other is stroking their ego to the max.
Also, communication gets screwy. No one talks straight or just says what they mean. Everything is full of sub-text and back-handed insults. People also start reading into everything you say, assuming you are playing the petty competition game along with them. For some reason that ties me up in knots. I couldn't care less about image and competition, but really just want to function and be able to cover monthly bills. I had to quit multiple times because I was getting nausea, headaches, etc.
My current environment has good and bad, but at least it is waaaay better than the adjunct scene. My boss has alienated most of my sensitive colleagues because she is very forceful and has a random micro-manage style. 95% of the time I get to work on my own, but occasionally I get something impossible thrown at me or I get hollered at completely unfairly, but I'm okay with it. I've just recalibrated to knowing that the random sucker punches as just part of it, and that most of the time it's fine.
The bottom line I've found is that most human beings are difficult to work with, especially work for. One does best to find a job where you mostly work on your own to minimize the negativity. I'm working even more in that direction by working to sell more of my work online, and to teach online. Even online you get some entitled jerks, but it isn't as hard to deal with as the face-to-face angry encounters.
I completely support people leaving any job that makes them sick and to keep trying until you find something tolerable. One has to be realistic, so any job will have negative aspects and bad days, but if the job hurts your health, then get out for certain. Everyone deserves that choice, even if it results in some debt.
