'A'isha Radiyallãhu 'anha narrates that a man sought permission to see Nabí (saw). He said: He is a bad son of his tribe, (or he is a bad man of his tribe) and then said: Let him come in. When he came in Rasúlullãh (saw) talked to him politely. 'A'isha Radiyallãhu 'anha asked: O Rasúlullãh! You talked to the man politely, though verily you said about him what you said. He said: The worst man in the eyes of Allãh. On the Day of Resurrection, will be he whom people avoid meeting, because of his wickedness.

(Abu Dawúd)

Note: Rasúlullãh (saw) said these words to record the truth so as. To save people from his evil, and as such cannot be considered as backbiting. However he spoke with this man politely to educate us, how to behave with such people and perhaps to rectify this person. (Mazãhir Haque)