I had never heard of the Black Crackers. Neat!
Here in sunny(usually) Florida many people think that the term came from the early cattlemen's use of cracking whips to keep the herds together during cattle drives.
I recently heard a teenager express anger at being called a cracker, first I knew of that. Most of us whose families have been here a few generations take "cracker" to mean a native Floridian, of which there are quite a large minority.
Some think it a compliment, meaning that today's true crackers carry on the resourcefulness and uprightness of the pioneer settlers. I mean the real pioneers, not the land barons. Sometimes the "damn yankees" thought crackers were backward and somewhat shiftless, and some were, but not all. If anyone tried to insult me by calling me a cracker, it wouldn't work!