This seems to say there is a limit to free speech
>The act of shouting "fire" when there are no reasonable grounds for believing one exists is not in itself a crime, and nor would it be rendered a crime merely by having been carried out inside a theatre, crowded or otherwise. However, if it causes a stampede and someone is killed as a result, then the act could amount to a crime, such as involuntary manslaughter, assuming the other elements of that crime are made out.
Your own link says that if you yell fire in a crowded space and people die you can be held liable.