One of the major themes in William Shakespeare's Othello is the relationship between seeming (appearance) and reality (being). Iago's plot is to use misleading appearances to convince Othello that his good friend Cassio and his wife Desdemona as having an affair. Othello's jealousy causes him to mistrust his wife, and develop the pangs of jealousy that eventually drive him mad, itself a mental condition characterized by inability to distinguish appearance and reality.
Although Iago is the main plotter and deceiver of the play, he may too be deceived. He says:
Though I perchance am vicious in my guess,
As, I confess, it is my nature's plague
To spy into abuses, and oft my jealousy
Shapes faults that are not—that your wisdom yet,
From one that so imperfectly conceits,
Would take no notice, nor build yourself a trouble
Out of his scattering and unsure observance.
Thus Iago's hatred of the Moor itself is rooted in his own jealous nature and not based in reality.