You actually can yell fire in a theater. If someone panics and gets hurt, then you can and should be held responsible for what happened. That case was overturned a few years later.
As far as threats go? It depends on the circumstances. Too many are being treated as zero tolerances so you end up with someone who wrote a story for a class project getting arrested because the teacher decided it was a threat. Public comments on a facebook page, specific statements against a school or person should be treated very seriously. Generic statements like "Sometimes I just want to kill the customers" may need a welfare check or a "be careful what you say" warning. People do vent. Venting is good for you. Keeping all the rage bottled up is unhealthy.
Stand by for political rant that no one else really cares about.
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My FS type is Steel with Magneton, Forretress and Bronzong.