[defen]

You're allowed to shout that there's a fire in a crowded theater if there's actually a fire. No one has ever argued that there is an unlimited right to say whatever you want whenever you want (libel and slander laws exist and don't seem to be controversial). If you falsely shout that there's a fire and cause a stampede and people are injured and it can be proven that you did it with malicious intent, you will be prosecuted or sued, but this isn't fundamentally different than libel or slander laws. Finally, you should know that the "fire in a crowded theater" phrase came from a unanimous Supreme Court decision that endorsed censorship and suppression of speech that criticized conscription during World War 1.