actually i have been thinking about this some more and i want to add on to it:
abuse in caregiving professions (like teaching or nursing) is not solely a result of power dynamics. it's also because people who go into those professions often have a idea of themselves as Good People, and are consequently incapable of recognising or acknowledging when they've hurt someone else. instead, they mentally put 'people who have inconvenienced me' into the Bad People box so they can freely abuse them while maintaining their moral high ground.
i read ross greene a lot when i was working with "difficult" or "behaviourally challenged" children. his refrain is "kids do well if they can" - meaning, in short, that most kids act out only when the demands of a situation exceed their capabilities. punishing them for this is not only cruel but also completely pointless, because they also don't want to be doing what they are doing.
a teacher who believes that there are two categories of people - Good People who Mean Well, and Bad People who Cause Problems on Purpose - is not going to see it that way. they're gonna put themselves in the first category, and the misbehaving kid in the second category. and once they have effectively depersoned the child and placed themselves on a pedestal, the world becomes simple again. because abuse is something that only Bad People do.