"The founding fathers mistrusted government power, and they had very good reason to, as do we. This is why they tried to institutionalize the separation of powers, the right to think, the right to speak, to be heard, to assemble, to complain to the government about its abuses, to be able to vote or impeach malefactors out of office.
John Stuart Mill talked eloquently in his essay "On Liberty" on the importance of free speech, of vigorous interaction. Let me just make one quote here from On Liberty:
"The peculiar evil of silencing the expression of an opinion is that it is robbing the human race; posterity as well as the existing generations, those who dissent from the opinion still more than those who hold it. If the opinion is right, they are deprived of the opportunity of exchanging error for truth. If wrong, they lose what is almost as great a benefit: the clearer perception and livelier impression of truth produced by its collision with error."
Despite our best efforts, some things we believe are probably wrong. We certainly are very keen on recognizing the errors of past times and other nations. Why should our nation, why should our time, be different? If there are things that we believe, if there are institutions in our society that are in error, imperfectly conceived or executed, these are potential impediments to our survival. How do we find the errors? How do we correct them?
I maintain: with courage, the scientific method, and the Constitution. Sooner or later, every abuse of power must confront the Constitution. The only question is how much damage has been done in the interim."
Carl Sagan "Science and Civil Liberties" (ACLU of Illinois Lecture, 1987)