Some people have way more power over others than they should.
Having too much power over another person is always harmful to that person. Even if you’re good. Even if you’d never intentionally misuse it.
Sometimes this plays out between groups. For instance, if you’re white, you virtually always have a kind of power over people who aren’t that no one should ever have over another human being. That’s not always the most important power dynamic in a given interaction, because real situations are complicated and there are a lot of different privileges (as well as power dynamics that aren’t reducible to privilege). But it’s still always *there*. (Some other dynamics that are also always there: male/not male, cisgendered/trans*, disabled/not disabled, intellectually disabled/not, poor/not poor. These are examples. It is not an exhaustive list. There are many dynamics like this, and many of them have not yet been named.)
And the power dynamic is long-term, it’s been that way for generations. And there are deep-running wounds that are going to take many generations of concerted effort to heal. You can’t make that go away by your good intentions.
You can be good to others; you can and should learn how to treat people well. But you can’t, on your own, fully undo the power dynamic and the harm it does. And part of the way to be good to people involves understanding the position you’re in, and being aware of the power you have and the obligations being in that position creates.
If you ignore the power you have, or pretend you can make it go away by being a good person, you will harm people in ways you could otherwise avoid. (One instance of this is constantly talking about how you’re checking your privilege – it doesn’t actually work that way. That tends to turn into flaunting unjust power, even when it’s done with the best of intentions.)
If you want people to treat people right, you have to understand and be willing to face the consequences of the power you have.