Those who would set limits to free speech , invariably come up with the same hackneyed reference, i.e., "you can't yell fire in a crowded theater".

As others have pointed out, this is a fallacious statement. If there actually IS a fire, you would endanger lives NOT to advise others that a fire is raging. And, if a play is being shown, and hollering "FIRE" is part of the play, of COURSE you can yell fire in a crowded theater.

I've personally been in a crowded theater and seen a character in a movie yell "FIRE" and no one stopped the movie for the yelling of same.

So, when you hear an opponent of free speech making this ludicrous statement, just be aware of the limitations of their knowledge, and the overall incorrectness of what they say.