It shouldn't be ok to incite mass panic (yelling fire in a crowded venue)
It shouldn't, huh? How about statements like "President is a war-criminal" or "He is not a natural-born citizen" — can such speech not some day be banned under the same doctrine? Because it does interfere with the government's efficiency and, consequently, the entire country's quality of life, does not it? We might think this ridiculous today, but many countries — including the various worker's paradises — consider insulting the Dear Leader a felony already. Don't you recognize a slippery slope while sliding down on it?
There is a movement to ban "hate speech" already. The entire Yik Yak app is banned on many campuses and today's students are being trained to accept such a ban already, so it can not be far away, that the thought-police spills out from those institutions into the rest of our world.
For the past 7 years, the number one rebuttal to any critics of the current President was that they are "haters". Do you think, we are far away from the sitting President becoming off-limits for criticism? We aren't — and it all started, when we were sold the bogus premise of "some speech ought to be illegal"...
It is naive to think that complete, and total, freedom of speech was ever intended.
Is it naive? Then I share my naivete with Benjamin Franklin, for example — a Founding Father — who considered any abuses of the freedom of speech to be a lesser evil than entrusting anyone the power to suppress them. For example:
Those abuses of the freedom of speech are exercises of liberty. They ought to be repressed; but to whom dare we to entrust the care of doing it. An evil magistrate intrusted with power to punish for words, would be armed with a weapon the most destructive and terrible. Under pretense of pruning off the exuberant branches he would be apt to destroy the tree.
Do you honestly believe, the fine magistrates of the 21st century Virginia would've helped calm Franklin's fears of that "the most destructive and terrible" weapon?