Up against the Wall, 12-Letter Compound Expletive

What is it about a certain 12-letter compound expletive that is, or used be, strongly associated with the black lower class? I know this might seem silly to most people, but it is worth a half-ass exploration, motherfucker.
There have actually been books published that surmised that the word's popularity had something to do with actual reality in the South. So many of a servant's brothers and sisters had been conceived with a white landowner that they indeed were motherfuckers. Or so the explanation goes.
Of course, it is now used in so many ways that the genesis of the word is hard to come by (pun unintended). The word can be used as much in admiration (that's one bad-ass motherfucker) as in revulsion (that's one bad-ass motherfucker).
Let's take a look at the white landowner thesis. According to it, blacks under sharecropping were worse off than during slavery. At least a slaveowner had an interest in his slaves' physical health. The owner of a plantation had little; if one black sharecropper dies, another will quickly replace him. If the owner takes a sexual interest in the sharecropper's wife, she had better be compliant with his demands.
All of this undercover hanky-panky revealed itself in light-skinned babies. Who later became the black upper-class by virtue of their skin color. In and around New Orleans, the racial mixing bowl was further complicated by the Creoles, who were usually of French/Spanish and black background (though not always). In the end, though, the Southern standard of being a Negro or black or whatever was one drop. Meaning if you had one drop of black blood in you, you were black.
There was a time, of course, that the word motherfucker could still shock. Maybe it was at first a way of separating yourself from mainstream white culture and "signifying" a certain derision for it. That's how long-time Detroit Mayor Coleman Young used it, referring to even high state officials as motherfuckers. He was showing he was still real or down or whatever you want to call it.
I don't think Obama's going to start tossing the word around anytime soon. Hopefully, he'll come up with what this country really needs, which are new obscenities, since the old ones don't shock anyone anymore. Believe in change!