US Supreme Court Justice Felix Frankfurter once said the right to free speech does not allow you to yell "fire" in a crowded theatre.
Firstly, that comes from Justice Oliver Wendell Holmes, Jr.'s ruling opinion from Schenck v. United States in 1919. And you left out one very important qualifier, the word "falsely". Even under Holmes, you could shout fire if it was true.
Secondly, you have left out that this was overturned in 1969, in Brandenburg v. Ohio, which limited the scope of banned speech to that which would be directed to and likely to incite imminent lawless action (e.g. a riot).
So, the speech has to both incite imminent action - not some theoretical future action - and that action so incited also has to be lawless.
So, while falsely yelling "fire" in a crowded theatre may incite imminent action - fleeing the fire - the action of fleeing a fire isn't lawless action. Therefore such speech would be perfectly legal.