Yes, because he has a pattern of staking out one extreme position and then doing something slightly less extreme; but both of which would have been unthinkable when laws and due process meant something.
And also, yes, because joking around is something you do on your own time and when you’re a child. Like not wanting your pilot to announce his intention to do some aerobatic maneuvers on an airline flight. Whether they carry it out or not is almost beside the point.
First, the situation itself is always serious, because because nobody in that kind of position should ever be "joking" about such a thing.
Second, this guy's not joking. A threat does not become a joke simply because it is weak/unlikely or delivered while chuckling.