Why are the people who are fighting Gaddafi's army called "rebels"?

Any group of people who oppose an organized government, would be in rebellion, thus those who rebel would be a rebel. It is neither a positive or negative connotation, but a classification. The people who deposed the leader of Egypt, were also rebels, but the leader Mubarak, was proven to be evil, to certain tribes, of his own people. I hope this helps.