Ta-Nehisi Coates’ writing at The Atlantic often hits the nail for me (thank you Izabella).
Here he discusses the fact that (contra Django) the sentiment of ex-slaves appears to have been significantly less vengeful than that of those who now feel on their behalf, and this leads me to wonder if there is a general pattern. (This thought may also be motivated to some extent by observing some of my own reaction to the recent Indian bus rape case.)
The righteous indignation that many of us so easily bring up on behalf of wrongs done to others (and the joy we feel in bringing or imagining horrible punishment down on those who have not harmed us directly) may be just the masterbatory exercise of an important component of the brain chemistry that underlies our capacity for altruism, but I wonder how much it shows up in other species which are also on the evolutionary path towards non-selfish morality. Do the monkeys which show anger when shortchanged in the sharing of treats also react on behalf of third parties? and to what extent might a tendency toward such reactions (even at a cost to the individual who has them) serve as an evolutionary advantage to the gene complex which drives it?