Throughout its history, the American government has had the unfortunate impulse to take away basic civil liberties in times of war and conflict. A wide variety of civil liberties have been temporarily removed in this way, from the writ of habeas corpus, to the right of civilians to be tried in a civil court. This has happened from the birth of this country to WWI to WWII to the war on terror. Although this is not a uniquely American phenomenon, it is worrying that America, a country that values highly civil liberties will quickly take them away if it considers itself threatened.
The justification for these temporary suspensions of civil liberties and the constitution is often based in a mob rule mentality. If taking away the liberties of one person can save hundreds of lives, taking them away is justified. However, our founding fathers subscribed to the idea that "power corrupts," and formed the government to counter this natural tendency. The impulse to take away basic liberties during times of conflict in practically every case went too far, because with no accountability the government will misuse its power. Almost always the government is caught up in a witch hunt, and all of a sudden convicting innocents sounds better then letting the guilty out on the streets. It is practically always the case that "Power corrupts, and absolute power corrupts absolutely." (Lord Acton, 1887)
Individual freedoms are necessary for a modern democracy to work properly. People must be free to criticize the government and hold it accountable. If this is taken away, the government is free to act without public accountability. Looking back, most Americans look poorly on impulsive restrictions on civil liberties like the Sedition acts, and Japanese Internment camps. Arbitrarily removing citizens civil liberties is against what this country stands for and must be prevented.
So why is it that an obscene number of civil liberties are taken time and time again from the American people in time of crisis? It is because there is a seemingly very persuasive case behind the equation.
Less civil liberties = more national security
However, almost all of the time the above equation is taken too far, and civil liberties are snatched away to combat a national security threat that is non-existent. This is because it is next to impossible to know exactly what civil liberties must be sacrificed to maintain national security.
The government will always want more then is needed and defenders of civil liberty, like the ACLU, will want too few. It is better to be on the side of the defenders of civil liberty, then on the side of those who have given into mass hysteria and are demanding more and more civil liberties should be given up. This is because practically all of the demands to give up civil liberties are unfounded and unnecessary.