Iago hates women. He half jokingly compares Desdemona and his wife Emilia to prostitutes, saying that they "rise to play and go to bed to work", and he thinks they are driven by base, sexual instincts. He is particularly obsessed with Desdemona's sexuality, and the "unnatural" nature of her relationship with Othello. In act 1, he characterizes Othello to Desdemona's father as a horse ("you’ll have your daughter covered with a Barbary horse. You’ll have your nephews neigh to you.") Iago's fixation on this perversion matches the perversion of his character. He thinks that everyone is either like him (that is, treacherous and self-serving) or a fool.

Another aspect of Iago's obsession with sex could be his own homoerotic tendencies. According to this theory, Iago hates women (and Desdemona in particular) because he wishes to replace her as Othello's lover. While this is not made explicit in the play, Iago does recount to Othello a bizarre homoerotic incident in which Cassius, asleep, mistakes Iago for Desdemona and kisses him (Cassius "kiss[ed] me hard, / As if he pluck'd up kisses by the roots / That grew upon my lips"). It's not hard to speculate that Iago's misanthropy is driven by a kind of self-loathing, and his obsession with female sexuality is an outgrowth of his own homosexuality.

In Othello, Iago is a misogynist from the beginning of the play to the end.  Quite simply, he sees women as inferior beings to men, and he has a hand in two of the three female characters' deaths in the play.

In Act I, Iago uses Desdemona to attack Othello.  He demeans Desdemona to her father, saying she is "making the beast with two backs" with Othello.  He uses sexual and animal imagery in describing her, suggesting that Iago believes women to be mere objects.

Once on Cyprus, Iago openly condescends to his wife and Desdemona, saying:

Come on, come on; you are pictures out of doors,
Bells in your parlors, wild-cats in your kitchens,
Saints m your injuries, devils being offended,
Players in your housewifery, and housewives' in your beds.

Again, he uses crude sexual imagery to describe women, even though they may be faithfully married.  His finishes off the exchange with a punch line:

You rise to play and go to bed to work.

This quote indicts Iago as one who believes women to be evil temptresses whose cruel nature is only to lure men into their lairs.  Critic A. C. Bradley agrees:

[Iago] succeeds very often with a mere hint—as, for example, the suggestion that Desdemona can not possibly escape the corruption for which the Venetian women (he implies) are notorious:

In Venice they do let heaven see the pranks
They dare not show their husbands.
[III. iii. 202-03]

Iago will use his wife to get to Othello as well.  He urges her to steal the handkerchief.  His plan almost works, but he understimates Emilia's outspokenness.  She calls him a villain after Desdemona is strangled, to which Iago responds, "Get you home!"  Again, he believes a woman's proper place is as a domestic.  When she persists in calling him a villain, Iago calls her a "villainous whore!"  These are the last words he says to her before he stabs her.

So, Iago is responsible for two women's deaths, Desdemona and his own wife's, which show his complete disregard for their kind.