If you shout fire in a crowded theater (in which there is no fire), and the crowd pushes and shoves to race to the exit (if it can happen at a Walmart on Black Friday it can happen in a theater where people don't want to burn to death), and people get injured or even killed, forget about morals, you could be liable for manslaughter.
Bad speech can be countered by MORE speech. Ban on speech cannot.
Did you honestly believe I meant to say that people should not be warned about an actual fire?
Regardless, you certainly do have the First Amendment right to shout fire in a crowded theater (the quote everybody refers is bad law), the government will not actively try to prevent it; you just may have to deal with the legal consequences of using your right in such a way.
Personally, I think shouting 'fire' in a theater should be 'free and legal' for a few key reasons.
First, it allows the morality of individuals in a society, not the morality of a few in power, to be the consequences of another's action. Second, if a bigot refuses service, shout's slurs, or yells 'fire' in a theater, it may hurt my feelings, but you bet your ass I want that information. By silencing people whose morals i disagree with, you don't change their morality. You only shield it from me, so now I don't know about it.