Acutally Justice Holmes, that's a private property issue.
If I own a theater, maybe I do NOT want to restrict speech...I've been to theaters where the audience is rowdy and yells at the screen. I've been to concerts where more problematic things than "Fire" have been shouted.
In the free market, people who don't like unrestricted speech/yelling fire will go to the Karen Theatre where you speech is restricted and you aren't allowed to bring your firearm etc.
Over time and equilibrium is established, and the govt stays out of it.
What a long, strange trip it's been, that 53 years after Woodstock that it's the conservatives that are championing free speech and "questioning authority" and the liberals want to shred the Constitution.
You CAN yell ‘fire’, if there IS a fire.
And yes, there is a fire.