He is not adding any information by calling him an idiot. He is expressing his disdain to those who seemingly agree that it was a silly choice. Those words are his argument. If Reuven found a crowd who considered anyone who voted against Obama as bigoted or against history (or whatever the fad was at the time), and he informs them that Shimon did so, then I agree.
While I was kidding about the statement being LH in and of itself, the point remains. But pray tell me how that was supposed to get you upset. (I mean, actually it did. But how?)