GEN1521 Even when praising someone, be careful not to mention his faults.   … Rashi comments on the butler’s statement to Pharaoh: “Cursed be the wicked, for even their goodness is not complete. The butler praises Yosef’s ability, but in contemptuous terms: “naar” (a lad): a fool, and not fit for greatness; “Hebrew”: he does not even know our language; “a slave:” and it is written in the statutes of Egypt that a slave cannot rule nor don royal garments.” Rabbi Yeruchom Levovitz commented that the butler actually meant to speak well of Yosef, for Yosef had been kind to him.   Nevertheless, a completely favorable statement will never emerge from the lips of wicked person.   Even when praising someone, he will off-handedly add a derogatory comment.  Every person should check his own behavior with regard to this pitfall.   When you speak favorably of someone, do you habitually add something unfavorable? (Daas Torah, vol. 1, p. 240).   PLYN 117-8