Othello is a notably heroic character, making his manipulated downfall all the more tragic. Although his nobility and honor are some of his primary characteristics, Othello is also a black man in a white man's world, and so, because of the prejudice of many of the the white characters in the play (most notably Iago), it would be more accurate to call Othello a "stranger."
Black individuals were often viewed as strange, rare, and/ or primitive in Shakespeare's time. Othello presents us with a robust contrast to this stereotype, defying prejudice with his nobility and honor. In many ways, Iago's scheme can be seen as a reaction to Othello's defiance of racist stereotypes. Indeed, though he's angry about being passed over for a promotion, Iago is also a white man trying to force a black man to fulfill a stereotyped caricature by provoking his jealousy and anger. In other words, Iago alienates Othello with his deception, forcing the honorable soldier to become a stranger to his community. As such, though Othello is a hero, Iago forces him to become a stranger and stay a stranger by using deception to alienate him from the white community.