In Plato's Apology, how does Socrates defend his practice of philosophy?

Socrates defends his practice of philosophy by stating that people misinterpret his actions. He tells his accusers that the reason he is too inquisitive is that he knows nothing. He is only trying to satisfy his intellectual curiosity by learning from those he believes to be wiser than him. He tells the story of the Delphic Oracle and how she claimed that Socrates was wiser than any other man that ever existed. Ever since his friend Chaerephon told him that story, he set out to find someone wiser than him and prove the oracle wrong. After Socrates talks to politicians, craftsmen, and poets, he is invariably disappointed because they are not as wise as they claim to be. He comes to the conclusion that he must be the wisest, since he seems to be the only one who acknowledges his ignorance. Therefore, his actions are not meant to dishearten or disrespect anyone; instead, they are meant to enlighten the ignorant mind.
http://www.sjsu.edu/people/james.lindahl/courses/Phil70A/s3/apology.pdf