In defense of free speech, yes, the protestors have every right to denounce the president's actions, unless it amounts to sedition. Second, of course property destruction, unlawful assembly, etc are not protected actions.
However, one of the most popular tactics of all time by opposing parties is to masquerade as 'agent provocateurs'. Now, I'm not saying that any of these mindless peaceniks are being manipulated by the good guys (conservatives) and goaded into unlawful activities, but if you pause to think about it for a second, what better way would there be to discredit a movement?
Thoughtful libs (an oxymoron) are already fretting; they know their goose is cooked and that Bush & Co. will be unstopable in 2004.