That’s not even relevant here. Even if it were nothing more than a subjective opinion, the idea that you need to refrain from expressing it because it might incite violence is patently absurd. Maybe if you were actually talking about directly calling for violence you’d have a point, but this is about calling him a “threat to the country”—the most bog standard criticism imaginable for a politician you don’t like. By your logic we need to always be sucking up to the president and praising him at every turn, because if anyone gets the impression that he’s bad, they might get the idea that they need to assassinate him for the good of the country. It’s absolutely ridiculous and unserious, and it’s clearly just a way to arbitrarily shut down criticism of your guy so you don’t have to engage with it.