In the first place the **question** is ludicrous (the only person I can recall ever using the expression "ain't be" was Andy Griffith). Amy Curry would be rolling over in her grave. She taught English in the Black community in the South for more than five decades -- at a time when educators were allowed to educate; and she would 'crack the knuckles' of any of her students who talked like Ms. Jenteal. Then along came the 'linguists' with their 'explanations.'
In the past, when educators were allowed to educate (and even now, in the part of the Black community who CARE whether our kids grow up to be able to compete in the corporate world or attend the best schools), the conversation would have been how to HELP Ms. Jenteal [improve her grammar, and verb construction], not how to 'explain' her. Do you have differences in how grammar is used in the Black community (or in other ethnic enclaves?]? Sure. Does that means we ignore and explain away the problem? Heavens, I hope not!