The claim that Othello is more victim than villain has been widely discussed and there are arguments for both sides.
Iago is a very strong character and unless he meets his match, it is hard to imagine being able to recognize and therefore counteract his deceitful and ultimately destructive personality. He is, after all, or so to be believed "honest, honest Iago." Othello truly believes that Iago is protecting him and trying to help preserve his honor. When trying to convince Othello of Cassio's (supposed) betrayal,Iago reveals his own treacherous nature
even when (he is) they are apparently referring to someone else. This only adds to the chilling, calculating nature of Iago.
Othello's failure to see Iago for what he is throughout the play reinforces the theme of appearance versus reality and Iago's ability to use Othello's weaknesses to his own advantage almost confirms that Othello will submit to Iago's schemes.
However, Othello betrays Desdemona and himself and everything he believes in and still does not question Iago. When Desdemona clearly has no idea what he is referring to, he does not stop to question Iago but questions the woman he loves and married. Even his own words "so sweet was never so fatal" (V.ii.20) are not enough to make him stop. When Desdemona protests
Some bloody passion shakes your very frame (V.ii.44)
he persists. Only after he has killed her does he understand the depth of what has happened and even then he seems to believe it is not his fault but Iago's because he trusted Iago and "loved not wisely but too well"(V.ii.345).
Strength of character is what Othello lacks. He may be fierce and brave in battle but he is weak and lacking in substance when it comes to love. This could be from inexperience and of course from having a trusting nature, believing in the basic goodness of others which is why audiences are inclined to feel sorry for Othello, rendering him the true tragic hero. That being said, however, if he believed in the basic goodness of others, where was his belief in Desdemona?
Insecurity is no excuse to commit a crime so heinous and unjustified against someone as equally trusting as himself. Othello justifies killing Desdemona to save her - "I can again thy former light restore"(V.ii.9) revealing more about his mixed up morals and how he places emphasis on matters of state rather than matters of the heart. Othello's confusion regarding right and wrong seems to have been his final undoing.