Perhaps the best quote you can use for this would be from Act V scene 1 when Othello finally has the showdown with his wife that has been promised for so long when he confronts her with the supposed knowledge that she has been unfaithful to him. Note in particular the way in which Othello tries to justify the murder that he is about to commit in the words that he utters:
Minion, your dear lies dead,
And your unblest fate hies: strumpet, I come.
Forth of my heart those charms, thine eyes, are blotted;
Thy bed, lust-stain'd, shall with lust's blood be spotted.
Othello's logic, although perverse, does have some kind of twisted reasoning behind it. Through the language that he uses to address his wife, he makes it very clear that her act of infidelity makes his murder of her completely justified and deserved. He dehumanises her by refering to her as a "strumpet" and the last line shows the poetic justice of her death. As lust has been responsible for her sin, it will be her lustful blood that will be spilt on the bed, which is after all the site of her infidelity.