He would not deny courtesy even to wicked persons. It is stated that a person came to his house and asked permission for admission. The Prophet (pbuh) remarked that he was not a good person but might be admitted.
When he came in and while he remained in the house, he was shown full courtesy. When he left Aiysha (ra) said, "You did not think well of this man, but you treated him so well."
The Prophet (pbuh) replied, "He is a bad person in the sight of Allah who does not behave courteously and people shun his company bacause of his bad manners."
(Bukhari, Sahih Bukhari)