I'm still learning this site (I ride the LiveCloud short bus, so don't clown on me y'all!), so I'm only now seeing this thread. I didn't think the ad was all that funny, but I wasn't offended by it either. If anything, seeing a young man defending his mom like that is positive, IMO. The only thing stereotypically "black" about it was that fact that the boy called her his "mama" instead of his "mom," and his vernacular is probably a large part of what made the commercial so much a favorite, especially among white people. We are correct to conclude that it wouldn't have been as popular if the characters were white. But this is one of those "so what" things for me. I don't see this ad as reinforcing any negative views of black people. Like DDouble said, any white person who sees anything to clown on in that ad already feels that way.
I see cultural "blackness" as something to be happy to see depictions of. I've seen white people clowning on depictions of African-Americans doing traditional African dances. It wasn't the depiction that was the problem; it was the white people who saw it as something to clown on. To the extent there are "black" ways being characterized on that commercial, I feel the exact same way about it.