One of the prerogatives of American citizenship is the right to criticize public men and measures — and that means not only informed and responsible criticism, but the freedom to speak foolishly and without moderation.

Felix Frankfurter (1882–1965) American jurist, teacher; US Supreme Court Justice (1939–62)

Baumgartner v. United States, 322 U.S. 664 (1944) [majority opinion]
    (Source)

Ruling that the government could not strip a naturalized citizen of their citizenship simply for expressing political views, such as admiration for Adolph Hitler.