Maybe I'm wrong but I hear a lot of people playing some serious headgames. Seems like what is coming across is that "Revenge is bad---unless you have very, very good reason". Put another way one could say "Revenge is good--- if you have a very very good reason". Either way what I think is coming across is that people want to put a Intellectual explanation on something that is emotion-driven. Emotions are not Thoughts and Thoughts are not Emotions. Intellect and Emotions are related or connected in some ways but are still very different. Maybe this is kind of confusing. Here, let me put this another way.
If you are in a situation where you think revenge is a viable alternative then maybe you should go ahead. Just don't kid yourself that what you are doing is all that different from what the person who injured you did. My thought is that you had better have a pretty heavy-caliber rationaliztion to get you by later in life when you finally have to face the fact that when push came to shove there was just that slender rationalization's difference between what you did and what the other guy did.
But now lets suppose that you DON'T do the revenge thing. Suppose you go and take the higher ground. Maybe the guy gets "karma'd" and maybe he doesn't. Maybe you learn about it and maybe you don't. Fact is, though, you are now caught in a kind of no-mans-land. You didn't take revenge yourself, but you also haven't been able to let it go, either. And you spend a lot of time dwelling on "what if---".
Fact is that the dynamic of Revenge actually has very little to do with hurting another person. It has to do with keeping your head occupied so you don't have to look at how you might have contributed to yourself getting hurt. BTW: Thats one of the reasons Revenge is so "hollow" when it finally happens. Sure you get that initial gratification, but then you have nothing to occupy your thoughts the rest of your life about what you might have done to get yourself into that situation in the first place. FWIW.
Best Wishes,
Bruce