This is actually a popular misconception. The decision where "you can't yell fire in a crowded theater" was from was actually overturned in almost entirety in Brandenburg v. Ohio in 1969. And even then, it was only an analogy, and never actually was the law. You actually, theoretically, CAN yell fire in a crowded theater. Websites on both sides of the isle have admitted it is a terrible analogy for defending censoring certain content for being potentially harmful. It is, quite literally, a legal myth. A legal myth that still affects our Congress today while they examine how to prevent the spread of misinformation [1].
https://abovethelaw.com/2021/10/why-falsely-claiming-its-ill...
https://reason.com/2022/10/27/yes-you-can-yell-fire-in-a-cro...
https://www.theatlantic.com/national/archive/2012/11/its-tim...
https://www.theatlantic.com/ideas/archive/2022/01/shouting-f...
https://www.whalenlawoffice.com/legal-mythbusting-series-yel...
https://www.thefire.org/you-can-shout-fire-in-a-burning-thea...
[1] For an example (out of many) of why regulating misinformation is legally almost impossible, see United States vs Alvarez, which ruled that the Stolen Valor Act of 2005 (which criminalized faking having a military honor) is legally protected speech and the act was a violation of the constitution. Since then it has been extended with a new 2013 act which requires intent to gain something by fraud, which hasn't been struck down (yet).