Shakespeare includes both positive and negative descriptions of women by Iago in these lines to show Iago's misogynistic and conflicted views about women.
On the one hand, Iago describes women in very disparaging terms, as deceitful, fickle, and lustful:
"Come on, come on; you are pictures out of doors,
Bells in your parlors, wild-cats in your kitchens,
Saints in your injuries, devils being offended,
Players in your housewifery, and hussies in your beds."
He sees women as putting on an act, as hypocrites who pretend to be virtuous but are wanton behind closed doors. This negative view reveals Iago's deep cynicism and distrust of women.
On the other hand, Iago also acknowledges that women have "a plentiful wit" and "an infinite tongue," indicating their intelligence and verbal skills. And he admits that men crave the love and attention of women:
"In truth, fair Montano, we men may say more,
Swear more: but indeed our shows are more than will;
For still we prove much in our vows, but little in our love."
So despite his professed misogyny, Iago demonstrates a grudging respect for women and an understanding of their power over men.
By including these conflicting views, Shakespeare suggests that assertions of misogyny often reveal more about the speaker than about the subjects. Iago's views tell us he is a conflicted and bitter character, prone to making cynical generalizations that reflect his own warped perceptions rather than objective truths. The contrast shows the complexity of human attitudes about gender and relationships.