Let me give you a personal example. My grandfather was a holocaust survivor, he managed to escape from one of the deportation trains going from a transit camp to what he suspected was a death camp. While hiding from the Nazis he murdered German colonists who had come as farmers to Poland. He did this to steal their food and undermine the German presence in the region before linking up with other cells and groups further east. This was quite obviously classified by the Nazis as murderous activity. I'd call it justified, I'd call it a blow for freedom.
I refuse to censure Mandela or his associates from contesting their oppression the way they did. Without the strategy of tension and violence which exhausted South African society it is unlikely that they would have won the final concessions they did as quickly as they did. The endless call up of reservists, the limitless military campaigns, the ceaseless attacks, the riots and assassinations, all foisted a siege mentality on South Africa that contributed greatly towards the final settlement.