The Framers knew, better perhaps than we do today, the risks they were taking. They knew that free speech might be the friend of change and revolution. But they also knew that it is always the deadliest enemy of tyranny. With this knowledge they still believed that the ultimate happiness and security of a nation lies in its ability to explore, to change, to grow and ceaselessly to adapt itself to new knowledge born of inquiry free from any kind of governmental control over the mind and spirit of man. Loyalty comes from love of good government, not fear of a bad one.

Hugo Black (1886-1971) American politician and jurist, US Supreme Court Justice (1937-71)

James Madison Lecture, NYU School of Law (1960-02-17)
    (Source)

The inaugural Madison lecture. Reprinted as "The Bill of Rights," NYU Law Review, Vol. 35 (Apr 1960).