Agreed. He can post whatever he wants, but he may also be searching for a new jobby job soon.
yeah happened at my old job. someones property went missing and someone posted "people working at X company are thieving bastards". got fired for that
I got a formal warning once for saying "X company issuing redundancies on Boxing Day, how very festive!" haha. they had printed it off on A4 paper blown up 4 or 5 times the size. lol.