I do have a negative opinion about managers. Managers mandated themselves into making x times the amount of their top paid report, control decision making, and have hiring and firing powers all in one position. Managers being people doesn't make them immune from criticism, and if me describing the status quo upsets you, then maybe we should be having a bigger discussion about what being in a captured ideology looks like from the ground.
Yeah, there is now only incentive to get rid of you since you are having a negative impact on the manager's (perceived) success, and you have also banned yourself from ever being promoted to management by being disloyal.
I'm curious where you work (not specifically, I'm talking about generally the industry), because it's not been my experience either as a manager nor my understanding of anyone else in silicon valley or large or mid sized software companies. I've managed engineers who get paid more than me, never have had unilateral hiring or firing powers, and don't control much decision making power other than my ability to hopefully influence engineers or upper management.
I could imagine your case being true in other places (finance, for example) where managers usually aren't engineers and there is much more of a fiefdom organizational structure, but it hasn't been my experience in software.
"We're all on the same level, so you can't hold us to a higher standard" is a silly but common way to confuse this sort of ethical problem.