The basic error of these sections is that they move in the direction of
suppressing opinion and belief. This would be a very dangerous course
to take, not because we have any sympathy for communist opinions, but
because any governmental stifling of the free expression of opinion is
a long step toward totalitarianism.
-- Harry S. Truman Public Papers of the Presidents
Truman, 1950 Veto of the Internal Security Bill. September 22, 1950
http://www.trumanlibrary.org/trumanpapers/pppus/1950/254.htm