What makes blackface offensive is the history, it was during the Jim Crow times when blacks did not even have equal rights and were not even treated like humans.
Nick Cannon is an idiot. I HATE black people who do stupid sh*t like this giving conservatives paint ball ammo to whine about being oppressed.
The truth is that white people really aren't offended by this though. They have never collectively been "made fun of" for being white. There is no history there and white people don't bond on "whiteness" unless they are being racist. Most would laugh at this. Being stereotyped as a lazy coon vs having good credit? Yes.....I'm sure this really hurt their feelings.
Also, this looks like Nick copied Emmanuel Hudsons "Sterotype (Black Kid White Kid)" video/idea.