In "The Year of Living Biblically" Jacobs describes asking someone he had learned was an adulterer if he could stone them. He then proceeded to toss very small pebbles at them to make sure he was following the proscription from the Bible. Nobody was harmed.
While his majesty the king is dining with the finest spices, public services break asunder under his ruinous savings. He won't even pay for a proper executioner anymore, he got replaced by a maschine any fool could handle!
Because the death of a person is terrible and should not be celebrated no matter the circumstance? Because killing someone in a flashy way unavoidably glorifies it? It's not a hard answer.