From japanese macaques to Romeo and Juliet to the crusades to the hatfields and mccoys, violence begets violence. I am not sure if peace begets peace or if nonviolence begets nonviolence, but the cycle of revenge seems to be a human (primate?) one. Perhaps it is the cost of having long memories.
I think the only way to make this world safer and more peaceful is to always push toward recognizing each other's humanity and dignity and to - as individuals as well as governments and cultures - to embrace justice over revenge and love over hate and over fear. Love, hate and fear are words thrown around so much that they have almost become meaningless. The examples who come most to my mind are the words and actions of MLK and Gandhi, as well as many of the words and actions attributed to Jesus and the Buddha. To seek both justice and understanding without giving into the human instinct(?) for revenge.