Anything short of "I'm going to kill a bunch of people" should only garner a close eye.
Whey they decide indirect threats are a threat....
...they validate dude's ranting.
Talk is just talk(1). Keep on talking, maybe get some scrutiny. But, until someone does harm, tossing them in jail or the loony bin is uncalled for and stalinesque.
Besides, why does this guy (assuming he is fruit loops) deserve 3 hots/cot and rubber room treatment? I've seen puh-lenty of folks more dangerous to themselves & others in serious need of life-long commitment get booted to the curb at hospitals.
I think I get it. He was arrested & sat on:
1. Because dude
wasn't so far gone, because he did have enough rationality to post on FB
2. Because his bluster was aimed not at regular folks, but at the King's Men
(1) Treason is an exception, as is assault against another person. That's about it for exceptions. Gov't is not a person, so it ought to suck it up and drive on.