While Othello was manipulated into murdering Desdemona, he was the one that had the physical choice. Iago constantly agreed with Othello, saying that Othello should kill Desdemona. This influenced Othello’s decision, but it was ultimately Othello that chose why he should or shouldn’t kill Desdemona. His choice was based off of his own reputation. He loved Desdemona, but after one rumor he decided to murder her because of what others would think. He believes “she must die, else she’ll betray more men” [V, ii, 6] and he later admits that he is “almost persuade[d] justice to break her sword” [V, ii, 16-17]. He tells Desdemona to “think on [her] sins”, trying to get her to realize that he would kill her for having an affair [V, ii, 43]. When he thought to kill Cassio, however, he was seeking revenge. He asked Iago, “how shall I murder him” [IV, i, 136]. It is more contemplated and decided than Desdemona. The contrasts between his thoughts on the two were considerable. Othello’s immediate thought about Cassio was “kill him” but he was more torn up about Desdemona. When explaining why he killed her to Emilia, he said “she turn'd to folly, and she was a whore” [V, iii, 146]. He didn’t care to listen to Desdemona. Othello killed her because he thought there was no other way to repair his reputation. He couldn’t live with the shame of an unfaithful wife. It was his honor versus his love, and he chose honor. This turns out to be the main theme of the story. If reputation were not a factor, Desdemona would not be dead.
In the end of Othello, reputation trumps all else. Othello killed Desdemona out of shame, making the murder an honor killing.