Who cares how he thinks of himself? He can think he’s Napoleon for all I care. The fact is he is not a king. We do not have kings here. We fought two wars to get rid of the kings and to keep them away.
The whole concept of a king is that he is not anybody’s servant, everyone else is his servant and owes him loyalty. In a monarchy the king is the state. “L’etat c’est moi”. That is why it is treason to plot to kill him or his heir, or to interfere with their wives. In this country the constitution specifically rules that idea out; even killing the president is not treason, because he is not the state, and no loyalty is owed to him.
But the whole question is irrelevant here, because in a country with freedom of speech one may curse even a real king without fear, so the posuk’s advice doesn’t apply.