The enemies of free speech are coming out of the woodwork in response to the violent protests breaking out in the Muslim world. It all started with the Innocence of Muslims trailer on YouTube and the later Mohammed cartoons appearing in the French magazine Charlie Hebdo — which was firebombed over similar concerns a year ago. The wave of pro-censorship views presents an opportunity to audit the two most-cited arguments offered by those who oppose the free exchange of ideas.
"You can't shout 'fire' in a crowded theater!"
This sentence is the proverbial duct tape of alleged exceptions to free speech. It is employed by the laziest of censors to nearly every controversy (and boy, it is used often), which basically argues, "There is an instance in which I can imagine speech I would want to punish after the fact, and this is license to suppress all speech I don't like."
Better, equally wrong, writers know that this sentence resembles a line from Justice Oliver Wendell Holmes' opinion in Schenck v United States. The argument (or fallacy) they present is as follows: "This case demonstrates that the First Amendment has limits to free speech, and if you can't yell fire in a crowded place, then many kinds of censorship are probably fine."
However, these would-be censors don't seem to know what the case was actually about. Justice Holmes wrote the infamous line not to imprison a man who caused a panic, but to justify imprisoning a man who wrote an anti-draft pamphlet during World War I. Not only did the opinion shamefully contradict the basic tenets of the Constitution, it is not the law of the land. The opinion did not stand as binding precedent for long, and current law would have the Court rule in favor of Schenck. Whether or not one can shout fire in a crowded theater has no bearing on legal exceptions to the concept of free speech as provided for in the First Amendment.
For a longer, better look at the history and misuse of this "exception" see Ken White's post.
Free speech doesn't include incitement or advocacy of violence
Despite the plain language of the First Amendment ("Congress shall make no law"), this argument contends that speech which advocates violence, later incites violence among sympathetic listeners, or eventually causes violence because of offense to listeners (intentional or not), are not protected. It is related — rhetorically and legally — to the shouting-fire argument.
Most of the people who make this argument — and everyone who is making it in regard to the Innocence video — are citing a legal doctrine that does not apply. The case that decided this issue, Brandenburg v. Ohio, created a two-part test to determine whether or not speech constitutes incitement and is therefore not protected by the Constitution: 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.
Not only does the threat of lawless action have to be imminent, but advocacy of violence is specifically held as protected speech. Brandenburg held that a speaker at a Ku Klux Klan rally was well within his rights to call for violence against minorities. Further the "Innocence" video does not advocate for the use of violence.
No one who has given this more than a few moments of thought should be surprised by the ruling. Advocating violence is routinely the business of statesmen, talking heads, pastors, law enforcement officials, and opinion writers. After all, articulating a pro-censorship view is itself speech that advocates violence, as Jason Kuznicki pointed out. That is, those who favor censorship are advocating for the state's agents to use violence, or the threat of violence, to suppress certain kinds of speech or to punish speakers after the fact. See Glenn Greenwald and Calvin Massey for more on this case.
Legal confusion aside, censorship advocates fundamentally misunderstand the very concept of free speech. Free speech isn't about the content or categories of ideas. There is no responsibility to use this freedom prudently. Free speech is a general prohibition against responding to speech with violence, whether that violence takes the form of individual retaliation or the form of rules and punishment from the state.
Advocates of censoring offensive, violent, or blasphemous ideas imagine that they are carving out small areas in which the state can play a role, while keeping benign speech out of the reach of censors. In reality they are creating an apparatus of general oppression, the application of which is limited only by the restraint exercised by the bureaucrats in charge of censorship. There is no way to create a power to suppress speech without risking the tendency for expansion seen in all government functions. After all, the quintessential case cited by proponents of censorship, Schenck, was itself a clear-cut example of protected political speech being punished by the state.