One of the protesters, David Swanson, has gone online to explain his behavior, saying
When Bush opened his mouth to speak I shouted "Defend the Constitution, Impeach Bush!" I repeated that several times, as people nearby knocked me over, cops handcuffed me, people gave me smiles and thumbs up signs. They threw me out and a couple of more defenders of our Constitution behind me, and then a few more, and then a few more. The handcuffed citizens who'd done their duty kept coming down the hill. They did not arrest us but did give us a ride down the mountain where we joined a crowd of protesters in the road who greeted Bush's limo coming and going.