Othello's destructiveness—and his determination to punish Desdemona for cheating on him—stem from his rage that Desdemona's immoral actions have also damaged him. What makes Othello so furious, Garber suggests, is that, when it comes to himself, Othello is a perfectionist. This all reflects pretty poorly on Othello.
But let's take a step back. Why is Othello a self-obsessed perfectionist in the first place? Othello's dangerous perfectionism may stem from his position as being consistently viewed as an outsider, simply because he's a black man in white Venetian society. Othello only could have risen to his position of power through incredible self-discipline.