If ye can’t trust a pirate, ye damn well can’t trust a merchant either! 

Take what you can, give nothing back – Pirates of the Caribbean

You can always trust the untrustworthy because you can always trust that they will be untrustworthy. Its the trustworthy you can’t trust. – Captain Jack Sparrow                              

                    Source : http://www.coolnsmart.com/pirate_sayings/