Not sure what you are saying here at all? It is not in the first amendment to protect anyone from instigating or encouraging injuries/death to another. They could arrest and detain him and confiscate his computers and start an investigation if they wanted, that just costs more, so they likely are following a protocol of dumb fuck says dumb comment. Start remote investigation. Find something more, make sure he knows they’re aware. If he persists things will escalate
If you hear 5 people yell at 5 people then they take a vote and the vote comes out 101 to 5 and the rest staying silent (hypothetical), it’s different than 53-53. It helps you understand what others believe/support while not having to listen to all of them talk.