A function of free speech under our system of government is to invite dispute. It may indeed best serve its high purposes when it induces a condition of unrest, creates dissatisfaction with conditions as they are, or even stirs people to anger. Speech is often provocative and challenging. It may strike at prejudices and preconceptions and have profound unsettling effects as it presses for acceptance of an idea.

Writing for the court, Terminiello v. Chicago, 337 U.S. 1 (1949). - Judicial opinions