That is patently loving stupid, and just screams of excuse-making. If you grab any black guy off the street and ask him what language he speaks, I guarantee you one or two smartasses will say this. The rest will say "English", or whatever foreign language that exists.
It's not 'excuse-making'. The reason why they will say English is because AAVE is not a separate language, it's a dialect. There are English creoles that are even farther from General American English than AAVE, but they're still English.
I'm sorry dude but linguistics doesn't support the theory that black people suck at grammar. They're speaking a dialect just as valid and consistent as yours.
Think of it this way: if it wasn't for people screwing up language over and over, you wouldn't have English.