Why blame him for what he critized others for? Here's a guy that tried to show how people's ethics are hung in mid-air and then for that we join the Athenians and make him drink hemlock for another 2500 years?
He did realize that ethics are objective (unlike epicureans), but he did not connect them to a source. I'm not criticizing him, just pointing out a simple fact. Ayn Rand objectivists do the same thing! They say certain objective ethical rules exist - but can't name the source! In that sense, Socrates was like Ayn Rand, but the similarity ends there. Ayn Rand has no personal or sexual morals from what I understand, and her ethics were quite compartmentalized. At least Socrates ethics covered a wider spectrum of the human existence.