The Cask of Amontillado

This story grabbed me by how violent it was. The tale is dark and a good example of Montresor feeling like he is the judge, jury and executioner to Fortunato. He is angry at him and deceives him with wine and the thought that he has a rare kind in the catacombs of his house. My first thought about Fortunato actually going down in the cellar with Montresor was that the costume he was wearing was kind of ironic. He was dressed as a jester and now he was falling for the evil plan. But why Montresor is so hurt just by a simple insult i'm still confused why he would go so far as to kill the poor guy.