He thought they were saying Booo-ush.

Report from Opening Day:

President Bush is never more likable, engaging or, frankly, informed as he is when he's talking about baseball. He lights up, displaying a breadth of knowledge that, uh, we never sense when he's discussing the Al-Anbar Province. He threw out the first pitch at the new Nationals Stadium last night and was, predictably, booed. We almost — almost — felt bad for him.