As ususal, T.L. Davis has an excellent piece over at his place.
Please, go RTHT.
I always thought the phrase meant a person or persons who were at odds with society, and dangerous to society.
TL turns the meaning around with something so obvious I felt like I just got clobbered with the fabled "Clue-By-Four".
On a side note, when I worked at DirecTV we used to joke about how somebody would change the title to a movie to make it more "relevant" to the foreign audience.
When Will Smith's "Enemy of the People" was playing, and we were broadcasting it to South America, the tile had been changed to "Public Enemy".
A subtle change to some, but considering how corrupt most South American governments are, it was a telling change.