. . . but it damn sure makes it even. We can disagree on who is right and wrong 'til the cows come home, but we can usually agree on who won. How often do you hear people criticize the Nazi war crimes trials, even though they were being tried for violating laws which had not previously existed? By some people's value systems (a number of them, actually, and not all of them ranting racists or neo-Nazis), it is wrong to convict people using ex post facto laws, but we seem to have done pretty well with that "wrong". And what about the US Civil War? Some consider it to have been a violation of states' rights, but it brought about an end to slavery and a stronger nation.
To a number of people, myself included, a stronger nation is not a desireable thing, but to others, this was a positive from that conflagration. Few people lament the loss of slavery.
This creed is really mostly going to be observed by those who have some sort of spiritual or religious view, I think. Responding to a wrong with another has paid dividends for people before, though it may come crashing down around the heads of their descendants. Responding to evil with evil is a prime indicator of a person who believes in materialism. Note that I did not say that "materialists all believe that responding to evil with evil is okay," only that only a materialist would actually respond to evil with evil. This is of some interest to me, for, as we see in the world today, many people calling themselves godly perform actions which are obviously intended only for benefit in the material world. They isolate their religion and put it in a box, separated completely from their actions.
In my opinion, the two camps most steeped in this sort of destructive materialism are 1) some religious zealots, and 2) some Objectivists. They seem to be the people who are perfectly willing to kill everyone in the world about whom they have any uncertaintly. They are the two most visible groups espousing the "if you aren't for us, you're against us" mentality, and their willingness to committ atrocities to further this purely material desire seems to have no limits.