Dissent is not unpatriotic. It's important to learn about the flaws and blunders of American history. It is patriotic to dissent about it's current mistakes and it's dark sides. America should not attempt to conceal it's mistakes and flaws from either the world or it's own citizens. We have to recognize the flaws before we can address them. I'm no big fan of Bill Clinton, but he said "There's nothing that's wrong with America that can't be fixed by what's right with America." And one of the things that is 'right with America' is the right of the people to protest, dissent, and change America. Slavery's end, voting rights, workers rights, etc. etc. have all come about because the American people had the right to push against the status quo. Unpopular wars can and should be railed against and stopped.
It is false patriotism to adhere to the "America, love it or leave it" mentality. Those who adhere to this turn a blind eye to America's faults. How will we ever address them if we do not allow ourselves to even see them?