They're trying desperately to recapture the feeling of what many thought to be the best times of their lives (in the late 60's), but just can't seem to come to grips with the fact that their youth is long gone and Woodstock is over.
Btw, if a Rat Prez were currently in power and had conducted the war in Iraq exactly as Bush has done (a big if, I'm well aware), these protests wouldn't be happening, and the leftists would be praising Iraq's liberation like there's no tomorrow. This is all about partisan politics and nothing more.