Why has machiavelli’s the prince evoked so much discussion and controversy? what do readers find enlightening, horrifying, or disturbing?

Many people found it disturbing because of the methods that he suggested for staying in power as a ruler. One example can be when he says that if you take down a king, you have numerous options what to do with his family. He further says that although there are many ways to handle them, history has proven that the most effective is to kill everyone, which made the people call him evil or much worse. He does not however state that this is his belief, but rather that this is what successful rulers throughout history did, so it's kind of a misunderstanding.