Can someone be charged over a comment on a f.b fan page?

This is so stupid I cant believe Im asking this. But I can't put into words myself how to stop this. Someone made a joke and someone else got upset. The person that was upset claimed that it was a threat. It was a obvious joke. I stood up for the person who made the joke. Can someone charge another over remarks said in a open forum? That person is now claiming that they are "building a case" and we should all wait for a knock at our door. They claim that bc of the recent comments that that man made about blowing up a airport over twitter that we all should be more wary about what we say. Agreed I wont twitter about airports or airplanes. This person has also been very insulting and has been name calling. He called one person a stupid dirty Jew. If you put yourself in a forum such as a f.b page do you not open yourself up to disagreements and insults. You know going into it not everyone is going to play nice. Would this person have a case?