Is There a Right to Speech that Advocates Illegal Acts or Violence
In 1919 the Court said no. Indeed, it said that any speech that had a ‘tendency’ to cause a volation of the law could be punished. This principle was used to convict a Socialist for mailing antiwar leaflets.
In 1925 the Court established stronger speech protections, stating that speech could not be punished unless it presented ‘a clear a present danger’ of imminent harm. In 1931, this was used to overturn a conviction based on a California law. That law make it illegal to publically salute a red flag — the symbol of (violent) revolution.
In 1950’s during the second Red Scare, the Court backtracked saying that the clear-and-present-danger principle did not apply to speakers who advocated overthorwing the government, no matter how remote the danger of such an occurrence might be. (This paved the way for jailing policitial activists, loyalty oaths, etc).
In the 1969 case of Brandenberg v. Ohio, the Supreme Court struck down the conviction of a Ku Klux Klan member under a criminal syndicalism law and established a new standard: Speech may not be suppressed or punished unless it is intended to produce ‘imminent lawless action’ and it is ‘likely to produce such action.’ Otherwise, the First Amendment protects even speech that advocates violence. The Brandenberg test is the law today.
Here’s what Alan Dershowitz writes about the distinction between advocacy and incitement (_The Best Defence_ p. 222):
“Advocacy is the communication of ideas; it is directed at intellect; it affords the listener an opportunity to reflect on it. Incitement, on the other hand, … is a spur to automatic action, intended to bypass the rational thought processes. It is against this oversimplified background that the classic case of shouting fire in a crowded theater can best be understood. Shouting the word “fire” is not the communication of an idea designed for reflective thought; it is precisely the same as if a fire *bell* were intentionally rung. It is intended to spur an automatic series of responses.”