Haman knew that Mordecai was not willing to respect him as a chieftain in the empire. His original intention was to kill him but upon enquiry, he knew that he was a Jew. He changed his mind and decided to eliminate all Jewish nationality. Don't you do this at times when one of your children offends you; for a minor misunderstanding between you and your neighbours, don't you engage in 3 days dry fasting to deal with him or her. In everything, avoid overdo.