The infamous "shouting fire in a crowded theater" was mentioned by Holmes in U.S. v. Schenck which had nothing to do with fires or theaters. The case involved whether Schenck could be convicted under the Espionage Act for the crime of writing and distributing a pamphlet that expressed his opposition to the draft. That is the dangerous idea that sent a person to prison.
>...In 1969, the Supreme Court's decision in Brandenburg v. Ohio effectively overturned Schenck and any authority the case still carried. There, the Court held that inflammatory speech--and even speech advocating violence by members of the Ku Klux Klan--is protected under the First Amendment, unless the speech "is directed to inciting or producing imminent lawless action and is likely to incite or produce such action"
Even Holmes seemed to quickly realize that the Schenck decision was odious since in the same term, he also wrote:
>...In what would become his second most famous phrase, Holmes wrote in Abrams that the marketplace of ideas offered the best solution for tamping down offensive speech: "The ultimate good desired is better reached by free trade in ideas -- that the best test of truth is the power of the thought to get itself accepted in the competition of the market, and that truth is the only ground upon which their wishes safely can be carried out."
https://www.theatlantic.com/national/archive/2012/11/its-tim...