I'm afraid I don't feel I have much to contribute to this discussion without a lot of thought & study.
Except this and I think I saw at least some references to it in several places including the definitions offered themselves.
My first (and only at the moment) thought regarding oppression is that it's a side effect of unacceptable use of "power".
I recall putting out a common quote somewhere here in the past about "power corrupting".
In fact, a substantial part of my life has been involved in working against and educating people in general about the dangers of "power" - period. That's my personal "soapbox" which I don't feel belongs here although the ramifications in this lifestyle are considerable. Probably far more so than "oppression". A lot of it is very philosophical and heady stuff which I - for myself- just feel would be a bit overwhelming for here.
But I'll toss this out..............in a nutshell.
We ALL have power available to us in some form. We have to be extremely careful in the exercise of that power, and strive to understand what are often the far reaching effects of our power. Living with the awareness OF that power needs to be a daily affair. It's a lifelong challenge.