Back in the day, and not that long ago, there was something romantic about being an anti-war or anti-establishment protestor. For 5 or 6 years, it was at the level of a way of life in this country.
But what has happened in the interim is that certain groups (on both sides) have manipulated the "cause" emblem and used it to advance some singular agenda that more than irritates and annoys the bulk of us. And again that's on both sides.
On top of that, IMO the country is beyond the debate over whether the Iraq War is/was a good/bad idea, the surge, etc. People are just flat out bored with it and tired of the experiment if for no other reason than that we have so much else to worry about right now.
So when you see some young 20-somethings trying to make a spectacle of themselves and trying to disrupt (as if their meager numbers could) the Republican National Convention, they have the dual effect of just annoying everyone and making it even less fashionable to protest the establishment in the future.