From a reader:

Did you notice he gets this very basic point completely wrong? The reason you can’t shout “fire” in a crowded theater is not because people will be trampled, it is because, in this example, it is assumed your INTENT is to cause disruption.
If you shout “fire” and there’s no fire, it’s perfectly OK as long as you believed there was a fire, that your intent was to save lives.
Is there a more basic legal concept than this?