The thing is, 'you can't shout fire in a crowded theater' never really was the law - that was dicta from a Supreme Court case in 1921 about the Espionage Act and Justice Holmes was musing generally about the limits of free speech in a case where the Court upheld the arrest for violating the act with conduct (demonstrating against the draft) that would easily be considered free political speech by modern standards. I think it has stuck in the minds of people for generations because it's easy to understand and it's sensible . . . but it isn't really accurate as to the First Amendment when it comes to problematic misinformation. It's highly contextual.
The actual legal standard comes from a 1969 case that involved the arrest of KKK members in Ohio. In Brandenburg, the Court ruled that the standard for when violent speech is no longer protected by the First Amendment is when it is “directed to inciting or producing imminent lawless action and is likely to incite or produce such action”. Imminent is the key term - it can't be some generalized notion of violence.