An expression (a French idiom actually = politeness always) a classy and cool person says whenever he/she has the right (in a certain context) to be rude but does not use this very right.
A: Hey, B, Mr. X is such a asshole when talking to you ! Why don't you just tell him to fuck off ?
A Murderino life motto to remain Sexy and not get murdered. Not to be confused with being rude; more like, don't try to be so polite you put your ass in a dangerous situation that might get you killed.
You see a man in the middle of a dark desert highway with a flat tire. (No cars for miles) BUT he is wearing a ski mask and waving you down with a big knife in his hand .. fuck politeness , you don't stop.