Perhaps no part. The article states the government has been careful to back down when challenged in order to avoid that question being decided in court.
You can't use a bullhorn to make political speeches on a suburban street corner at 3am. You can't stand up in the middle of a concert to give a discourse on Hegelian philosophy. You can't use graffiti to express your dislike of the EMU.
And the "[falsely] yelling fire in a crowded theatre" was used in the decision of Schenck v. United States in 1919 to say that opposition to the draft during World War I was not covered under free speech. It was then used as cover to punish anti-government speech, and was overturned in Brandenburg v. Ohio in 1969. Quoting https://en.wikipedia.org/wiki/Brandenburg_v._Ohio :
> Finally, Douglas dealt with the classic example of a man "falsely shouting fire in a theater and causing a panic". In order to explain why someone could be legitimately prosecuted for this, Douglas called it an example in which "speech is brigaded with action". In the view of Douglas and Black, this was probably the only sort of case in which a person could be prosecuted for speech.