The New York Times has an article on how hard it for people to strike back at an offence in a appropriate way. By my reading it says that people are not perfectly empathic. People underestimate the pain they inflict compared to the pain the receive. I do not think this would be surprising to anyone, but most people do walk through life believing that when they retaliate they do so in an appropriate and justified way.
The results were striking. Although volunteers tried to respond to each other’s touches with equal force, they typically responded with about 40 percent more force than they had just experienced. Each time a volunteer was touched, he touched back harder, which led the other volunteer to touch back even harder. What began as a game of soft touches quickly became a game of moderate pokes and then hard prods, even though both volunteers were doing their level best to respond in kind.
Each volunteer was convinced that he was responding with equal force and that for some reason the other volunteer was escalating. Neither realized that the escalation was the natural byproduct of a neurological quirk that causes the pain we receive to seem more painful than the pain we produce, so we usually give more pain than we have received.
Research teaches us that our reasons and our pains are more palpable, more obvious and real, than are the reasons and pains of others. This leads to the escalation of mutual harm, to the illusion that others are solely responsible for it and to the belief that our actions are justifiable responses to theirs.
Clearly these cycles need to be short circuited before serious harm is done. This dynamic seems to apply all the way from sibling spats to international relations.