The belief that rules matter and that everybody has to follow them is the glue that binds a society together. It is much easier to tolerate injury when you know, deep inside, that the offender will be punished for his transgressions, no matter who he is.
But when you reach the point where you accept as fact that there are two different classes of people, those who get punished if they break the rules (you), and those who never will, regardless of their transgressions, rules very quickly cease to matter very much.
And when you know that the injuries you have suffered will never be punished by the law since your aggressor belongs to a Protected Class, then you’re left with precious little choice but to mete out the punishment yourself if any punishment is to be had at all. Also, if a certain class of the population doesn’t have to follow the rules, then why in the name of all that’s good and holy should you have to?