How may those who continue to oppress be brought to justice is an excellent question. I don't know the answer but I do have thoughts.

While their is a debate regarding corporal punishment for children, even those who agree with the idea of spanking entreaty parents to never spank while angry. I think that's a good start for society when trying to mete out justice; don't come from a place of anger.

People tend to gravitate toward groupthink. Many of Hitlers minions would never have committed the atrocities they did on their own accord; yet with a leader they did. The same with the native americans and slaves. It is also true that many of Martin Luther King or Gandhi's followers wouldn't have committed many of the acts of non-violence that they did on their own; yet with a leader they did. When we stand together against violence without meeting it with violence, we will be on our way. We will need a different type of leader.

As for how to bring them to justice...I have been taught that we are not punished for our anger, we are punished by our anger. Anger is a child of fear and living with fear is, as many here including myself can testify, is the greatest punishment.