Brand wasn't great in the interview, BUT, it's gone viral and people are listening to him. The message behind his arguments still came through, even though the substance was a bit naff. So this is a good thing, he's potentially hitting a demographic who would normally let this sort of thing pass them by.
That's exactly how the EDF started: a smart Alec mouthpiece for the disaffected masses becoming the figurehead of an antiestablishment movement badly disguised as politics. Che Guevara he ain't.