I hate to think this is going to turn into a racial thing, so I'm attempting to keep this on the up and up with a simple explanation of where the word ebonics stemmed from... the word EBONY, which is a hard black wood (Webster's) and can be used to describe someone of the black persuasion. Do white people know and speak ebonics? Absolutely! But, with the word ebonics deriving itself from the word ebony, it's fairly easy to see how it could be mistaken as referencing only someone who is black. I think that's where his explanation came from.
Conversely, I know plenty of blacks who speak with southern tongues... as well as Asians and Indians. What dialect you pick up all depends on where you grew up.
George
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George