He was trying to make sense of the situation. All he could determine right now was that Jack had severely fucked up and that he was literally this close to throwing him up onto the wall punching him in the head. Dean probably would have been ashamed of him for holding back, but Sam was trying to ride it out. He didn't want Kira coming back and bitching at him for this later on if it came back to bite him in the ass. No matter what his intention was, something usually did.