If you are neutral in situations of injustice, you have chosen the side of the oppressor.
"You can’t be neutral on a moving train," I would tell them. Some were baffled by the metaphor, especially if they took it literally and tried to dissect its meaning. Others immediately saw what I meant: that events are already moving in certain deadly directions, and to be neutral means to accept that."You Can't Be Neutral on a Moving Train: A Personal History of Our Times"
Let not any one pacify his conscience by the delusion that he can do no harm if he takes no part, and forms no opinion. Bad men need nothing more to compass their ends, than that good men should look on and do nothing.Inaugural Address at University of St. Andrews (1867)