When somebody does not realize what they do is wrong or offensive in general. Instead of apologizing, they will see themselves as the victim of the situation, no matter what they have done and the accusing person is deemed the offender.
It is a cause of ones ego to become so large that their remaining pieces of common sense start to decrease, turning you into a big selfish and arrogant dick.
Person1: My friend is always an asshole to me and my other friends, whenever we tell him that we don't like being treated like this anymore he just tells us to have some understanding
Person2: I assume he gets really mad too?
Person1: Yeah.. I don't understand why he never aplogizes but expects everyone else to.
Person2: He's got Atomic Tombustion then, tragic.