Opposite words for rude:
civil, elegant, humane, civilized, nice, delicate, late, tender, processed, refined, courtly, graceful, polite, later, urbane, cultured.
Usage samples:
  1. " I shall risk being rude in my rough way," said Barclay in a low voice, " and repeat my words.
    "The Master of the Ceremonies", George Manville Fenn.
  2. Mr. Faversham, I ask your pardon, that I was so rude.
    "The Mating of Lydia", Mrs. Humphry Ward.
  3. The gentleman I am with is a sort of cousin of mine and we don't get on very well; but I mustn't be rude.
    "An Amiable Charlatan", E. Phillips Oppenheim.
  4. And I am sure I beg your pardon if I was rude.
    "Not Like Other Girls", Rosa N. Carey.