Well, technically they are correct, “shouting fire in a crowded theater” is not an exception to the 1st Amendment, no matter how many people mistakenly think that it is.
It’s not an EXCEPTION but it is an actionable offense.
If people are injured or killed based on YOUR perfectly legal free speech, you are liable.
Just like you are liable for libel, slander, perjury, and other things that you have an absolute freedom to say.