Just saw the part of Seven Psychopaths where this was “disproven”.
Hans:
An eye for an eye leaves the whole world blind.
Billy:
No, it doesn’t. There’ll be one guy left with one eye. How’s the last blind guy gonna take out the eye of the last guy left?
In the same way, capital punishment discourages murder. Revenge has a strong evolutionary basis. Knowing that attacks may be avenged, discourages attacks.
Revenge has a strong and beneficial moral purpose.
However, revenge is most useful when it is directed at the perpetrator, not blindly applied to a group. Hitler initiated terror bombing of British cities in order to convince the British to end the war against the Nazis. When the RAF got the upper hand, they responded with area bombing of German cities. The Germans responded with terror weapons, the V-1 and V-2 (German, Vergeldung: reprisal), which are militarily worse than worthless, but killed thousands of British civilians. In the end no one was laughing, but the British had the last laugh: for every ton of explosives dropped on British cities, 350 were dropped on Germany.
No sane person wants a race war. If one comes, one side is much larger in numbers, better armed and organized, and far more competent in the application of violence.