I'll answer that one for rig while he is taking a break. In "mad about it," IT refers to the train wreck sentence. Rig means that if Obama can not comprehend that that sentence, standing on its own, was extraordinarily condescending and divisive, then Obama is not going to get the guy's vote.

The subject is important, and Obama and his supporters need to grasp the concept (I'm sure he does) unless he wants to be buried with Mondale and Dukakis and Kerry and . . . .