“Let us labor to add all needful guarantees for the more perfect security of free thought, free speech, and free press, pure morals, unfettered religious sentiments, and of equal rights and privileges to all men, irrespective of nationality, color, or religion.”

McCreary County v. American Civil Liberties Union, 545 U.S. 844 (2005) (concurring).

Charles Evans Hughes, De Jonge v. Oregon, 299 U.S. 353, 365 (1937).
Judicial opinions
Context: Freedom of speech and of the press are fundamental rights which are safeguarded by the due process clause of the Fourteenth Amendment of the Federal Constitution. [... ] The right of peaceable assembly is a right cognate to those of free speech and free press, and is equally fundamental. As this Court said in United States v. Cruikshank, 92 U. S. 542, 552: The very idea of a government, republican in form, implies a right on the part of its citizens to meet peaceably for consultation in respect to public affairs and to petition for a redress of grievances. The First Amendment of the Federal Constitution expressly guarantees that right against abridgment by Congress. But explicit mention there does not argue exclusion elsewhere. For the right is one that cannot be denied without violating those fundamental principles of liberty and justice which lie at the base of all civil and political institutions — principles which the Fourteenth Amendment embodies in the general terms of its due process clause. [... ] These rights may be abused by using speech or press or assembly in order to incite to violence and crime. The people, through their legislatures may protect themselves against that abuse. But the legislative intervention, can find constitutional justification only by dealing with the abuse. The rights themselves must not be curtailed. The greater the importance of safeguarding the community from incitements to the overthrow of our institutions by force and violence, the more imperative is the need to preserve inviolate the constitutional rights of free speech, free press and free assembly in order to maintain the opportunity for free political discussion, to the end that government may be responsive to the will of the people and that changes, if desired, may be obtained by peaceful means. Therein lies the security of the Republic, the very foundation of constitutional government.

Free Speech in Wartime (October 6, 1917)

Source: See For the Record: Selected Statements 1977-1980 https://books.google.com.br/books?id=wcx4AAAAMAAJ, Weidenfeld and Nicolson, 1981.

Source: Dictionary of Burning Words of Brilliant Writers (1895), p. 498

"The One Un-American Act," Speech to the Author's Guild Council in New York, on receiving the 1951 Lauterbach Award (December 3, 1952) http://ala.org/ala/aboutala/offices/oif/foryoungpeople/theoneunamerican/oneunamerican.cfm
Other speeches and writings

Campaign speech at Madison Square Garden (31 October 1932)

New York Times (November 28, 1954).
Judicial opinions