Yes, the First Ammendment garunteens us free speech. That freedom stops, when one decides to yell " FIRE " in a crowded threatre , for a " joke ".
If her son knew it was a joke, why didn't she know it was a joke? In fact, she did know. She also knew, given the public's mood, that she could teach those Muslims a lesson they'd never forget. If she'd done it to blacks or jews we'd call it racism. Because she did it to Muslims here on Free Republic we celebrate it.