The U.S. Supreme Court has issued six major landmark rulings on hate speech law since 1949.
Terminiello v. Chicago (1949)
Fr. Arthur Terminiello did for the Archdiocese of Chicago what mononucleosis did for kissing booths. A raging antisemite and right-wing lunatic, he gave a speech in Chicago that prompted protestors outdoors to riot. The city of Chicago arrested him under a law banning riotous speech, but the Supreme Court overturned his conviction.
[F]reedom of speech...," Justice William O. Douglas wrote for the 5-4 majority, is "protected against censorship or punishment, unless shown likely to roduce a clear and present danger of a serious substantive evil that rises far above public inconvenience, annoyance, or unrest ... There is no room under our Constitution for a more restrictive view."
Brandenburg v. Ohio (1969)
No organization has been more aggressively or justifiably pursued on grounds of hate speech than the Ku Klux Klan. But the arrest of an Ohio Klansman named Clarence Brandenburg on criminal syndicalism charges, based on a KKK speech that recommended overthrowing the government, was overturned in a ruling that has protected radicals of all political persuasions ever since. Writing for the unanimous Court, Justice William Brennan argued that "the constitutional guarantees of free speech and free press do not permit a State to forbid or proscribe advocacy of the use of force or of law violation except where such advocacy is directed to inciting or producing imminent lawless action and is likely to incite or produce such action."
National Socialist Party v. Skokie (1977)
When the National Socialist Party of America was declined a permit to speak in Chicago, the organizers turned to the small, ethnically Jewish town of Skokie—where 1/6th of the Jewish population was made up of families that had survived the Holocaust. County authorities attempted to block the Nazi march, but their efforts were overturned by the U.S. Supreme Court in a terse ruling. After the ruling, the city of Chicago granted the Nazis three permits to march; the Nazis, in turn, decided to cancel their plans to march in Skokie.
R.A.V. v. City of St. Paul (1992)
After a teenager burned a makeshift cross on the lawn of an African-American couple, the St. Paul Bias Motivated Crime Ordinance—which prohibited symbols that "[arouse] anger, alarm or resentment in others on the basis of race, color, creed, religion or gender"—came into effect. In a unanimous ruling written by Justice Antonin Scalia, the Court held that the ordinance was excessively broad.
Virginia v. Black (2003)
11 years after the St. Paul case, the U.S. Supreme Court revisited the issue of cross-burning after three people were arrested separately for violating a Virginia ban. In a 5-4 ruling written by Justice Sandra Day O'Connor, the Supreme Court held that while cross-burning may constitute illegal intimidation in some cases, a ban on the public burning of crosses would violate the First Amendment. "[A] State may choose to prohibit only those forms of intimidation," Justice O'Connor wrote, "that are most likely to inspire fear of bodily harm."
Snyder v. Phelps (2011)
Westboro Baptist Church has made a career out of being reprehensible. The organization, which came to national prominence by gleefully picketing the funeral of Matthew Shepard, later moved on to celebrating the 9/11 attacks and picketing military funerals. The family of Lance Corporal Matthew Snyder, killed in Iraq in 2006, sued Westboro—and its leader, Fred Phelps—for intentional infliction of emotional distress.
In an 8-1 ruling, the U.S. Supreme Court upheld Westboro's right to picket. While acknowledging that Westboro's "contribution to public discourse may be negligible," Chief Justice John Roberts's ruling rested in existing U.S. hate speech precedent: "Simply put, the church members had the right to be where they were."