If what you feel for people who have been involved in despicable events is contempt or hatred, IMO either your reaction is not rational, or you have not fully understood the sociological and psychological circumstances involved. The rational reaction to a despicable event, once it is understood, is to feel pity or sorrow for the people involved. Now, I'm not saying that one must always act rationally; but you seem to be saying that those who do not act rationally ought to be despised.
I believe that the feeling of contempt--that sense that others are less than oneself and ought to be despised--is the very emotion that is behind much (nearly all?) of the world's problems...including genocide.
