At $50,000 per hour, I'd do 40 hours of work for a hideous client.
We're not talking about murder or anything with risk to life. We're talking about dealing with assholes. There is a price (theoretically) that makes that OK, so long as it's time-limited. Of course, the client will almost certainly not agree to $50k per hour, but isn't that kind of the point?
I had a boss who was a bit too ... stressed ... for a while. You just couldn't reason with him about it.
In the end I solved it. I wrote in an email that he was just too stressed and really needed some time off, so he started to attack me personally.
I wrote to him then that he should take what he just wrote and show it to his parents or some other persons he had trust in, and ask them how he was doing. He finally realized he had behaved as a complete asshole for a while.
No, it wasn't a permanent solution. But he took a long, long, long vacation half a year later.
I might work for him again, but I'd keep a reserve plan and be out of the door quite directly. Life is too short.
Edit: Too small company to have an HR department. (I might add: I don't know if I succeeded, or he got himself under control when a quarter of the people quit and the rest had the CV out or at least updating it.)
In a small company, "the boss" is the owner and there is no HR. If you don't get along with him, you leave.
In a large company, HR's job isn't to help you but to keep the company from getting sued. They will almost always side with management. You might make a dent in a manager's reputation and, if 5 or 6 people come forward with the same complaint about him, he might be "promoted away" into a role with less direct people management... but you're fired by that point, so it means nothing to you.
HR is not your friend.
Your best move if you have a bad boss is to work out a transfer behind his back, and leave on good terms. Find someone with more clout who will request sponsor you. Don't "apply for" transfer. Get requested. Never say anything bad about your boss in the process, just that you're looking for work that's more relevant to your skill set.
We're not talking about murder or anything with risk to life. We're talking about dealing with assholes. There is a price (theoretically) that makes that OK, so long as it's time-limited. Of course, the client will almost certainly not agree to $50k per hour, but isn't that kind of the point?