Even freedom has limits. He threatens to shoot people - he goes to jail. If he hadn't been jailed, he'd then threaten an airline to test to waters. Would you be OK with that also?
But he didn't do that, he posted a sentence online. Postulating what 'he might do next' is how we got into the state we are in now. Every police department has a paramilitary swat team because when you kick in someone's door they might...., roadblocks are setup stoping drivers because those drivers might be.... Gvns and ammo must not be in hands of citizens because they might....
This guy didn't do anything, if the 'threat' needed to be checked out, that could've been done quite easily.
I am not a fan of pre-crime.