Now that Tarrok basically controls the city what does he have to fear, now he can show his true (insane colors)...I mean it is retarded that he would go so extreme so fast and add fuel to the fire but maybe that is part of his plan now he's forcing Amon to make a move and he feels like he'll be prepared.
Also I hate that he can blood bend I wonder if Katara taught it or if water benders just figured it out like fire benders learned to use lightning, Korra knew about it so I'm guessing that Katara had to have mentioned it.