"Whoever appeals against the law of his fellow man is either a fool or a coward. Whoever cannot take care of themself without that law is both. For a wounded man shall say to his assailant, 'If I live, I will kill you. If I die, you are forgiven'. Such is the rule of honor." -Opening for the Lamb of God song, "Omerta"
The phrase certainly doesn't exactly always apply.
I think the phrase was meant to say that you should always try to please thus customer, and thus he is always right apparently, or something like that.
Doesn't really apply to alot of situations though.