I cannot agree with that. Yelling fire in a crowded theater is, in fact, protected speech. Causing a riot, however, is not.
This meme came from Oliver Wendell Holmes’ opinion in Schenck v. United States. The actual quote, which people falsely paraphrase to try to make a point, is actually:
The most stringent protection of free speech would not protect a man falsely shouting fire in a theater and causing a panic.
Left out is the “falsely” part, as well as the relevant “and causing a panic.”
It’s instructive to understand what Schenck v. United States was actually about. In the case, the US government was prosecuting Schenck for protesting the war and the draft, and sedition against the interests of the government. Holmes’ used the causing a panic argument to justify conviction of Schenck for printing flyers criticizing the war.
The SCOTUS later overturned the decision, in Brandenburg v. Ohio. Thankfully the courts now recognize that the people have a right to criticize the government. I think it’s funny when people use the quote as some sort of argument that it’s okay for the government to restrict speech, but they would never think it’s okay for the government to jail people for protesting war. Yet, that’s what the quote was all about.