One major theme in Oedipus is that of the effects of pride. In fact, this play supports the maxim: "pride goes before a fall."
With these words, Oedipus shows his great pride. He wants to remove "this polluting stain" for himself, not for someone else and not for his city or its people. He is motivated purely by pride. His pride, of course, also led to the death of King Laius, creating "this polluting stain" in the first place.
His pride will ultimately lead to his downfall. In this case, his pride went before his fall.