It's not about blacks specifically though. That is the false assumption. The twins were spoofing urban
black youth, and a specific subsection of it at that. I've never known anyone
who acted as much like a urban ghetto or a country redneck as these two examples were played as. I've lived in the city and in the country and I've known both blacks and whites who leaned towards the stereotypes but neither was a full-on stereotype. It's still unflattering either way but since it's still more acceptable to dismiss racism against whites, it's just written off like the above.
You can't go and say one is about a particular race when it's clearly not, then turn around and say the other is about just a specific subsection of another.