Not sure I understand your point - yes the runner of the instance has the ability to do whatever they want, but that doesn't mean whatever they want to do is a good idea. If the decision is implemented my response would indeed be to move to a different less problematic instance, after complaining a bit to see if I could get the decision reversed rather than having to flee.

Actually, that could be the reason why sometimes the user finds things unacceptable, because some instance owners treat their instance like their "own little walled garden." It's a real pain to shop for an instance when you don't want a walled garden but rather an open medium through which to access content you wish to see. I see some instance owner decisions as reasonable (like staying away from misinformation and fake news) and I see others as a little bit unreasonable. I try to stay out of walled gardens. I like to roam free and make decisions for myself because I'm a smart boy, I know what I want and how I want it.