n0m, it doesn’t matter how wealthy or powerful he is, he is NOT a king. He is just another public servant, just like any janitor in a government office. There is no reason to respect him, unless you happen to think he deserves it.
And even if he were a king, there is no danger in cursing him, so yes, feel free to do so.
And TKM, your father was wrong. The whole idea is unworthy of a republic.