Why does Iago say he hates Othello

Iago says that he hates Othello because Othello passed himover in favor of Cassio for a promotion.

Iago has many reasons for why he hates Othello. None of them are his true feelings toward Othello. Iago hates authority and want to sabotage the authority. This characterization was also used in the Dark Knight when the Joker gave multiple reasons why he has many scars. They are chaos makers.