Sorry Dino, in my opinion, violence is not justifiable except as an IMMEDIATE act of self-defence against somebody, who is about to kill one. ALSO: I disagree with your view that revenge is a part of "human nature" and therefore should be "acceptable". In that case everybody would be killing everybody, because "injustices" take place all the time around us everywhere! Keeping the "beast" within us in check, is the challenge, which makes us grow closer to the likeness of the "Image of G-D" as CIVIL persons, who put their trust in the fact that there indeed IS a Justice System of the Universe as is acknowledged in the Asian philosophies/religions and in the JEWISH Scriptures (Eccl.): "Thus says G-D: restrain from revenge, for the revenge is mine, says G-D".
Pope Francis: Priests in Holy Year can absolve 'sin of abortion' (AP)
from the article: The bystanders