The problem is that if he gatekeeps something you need access to, you're obliged by that fact to have a relationship with him (unless you're able to remove him from that position).
Basically, because it's not an option to not have any relationship with him it's in your interest to get along with him as well as you can. The fact that he can and has hurt you can't be ignored, but what other option exists?
Since fight and flight are both unavailable as options, trying to get along with him to the extent you're capable of is the only real remaining option.
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I was ashamed of myself when I realised life was a costume party and I attended with my real face
"Many of us like to ask ourselves, What would I do if I was alive during slavery? Or the Jim Crow South? Or apartheid? What would I do if my country was committing genocide?' The answer is, you're doing it. Right now." —Former U.S. Airman (Air Force) Aaron Bushnell