I also agree that there are astrologers that give bad advice as well as doctors who give bad advice.
There are ways of telling the difference between real doctors, and false or bad ones. There is no way to tell the difference between "real" astrologers, and false ones. That's the same as trying to differentiate between "real" psychics and false ones.
Since no one has brought it up yet, prove that astrology can make accurate predictions of future events, and win a million dollars! http://www.randi.org/research/index.html