Man, this is painful.

Washington Post:

The first pitch of the Washington Nationals' second season at Robert F. Kennedy Memorial Stadium was low and away, bouncing in the dirt before being scooped up by catcher Brian Schneider. For that, Vice President Cheney received a round of boos from the home crowd this afternoon.

You see? The booing happened because Cheney missed the strike zone.

Reuters:

The vice president, whose popularity is slumping along with that of President George W. Bush, walked out on the field to cheering and booing from the near-sellout crowd. The boos appeared to be little louder than the cheers at RFK Memorial Stadium.

Now go see video at the Washington Post's own site and see how many "cheers" you can hear. It's not even close. It sounds like a riot is about to break out.

(Via FDL.)