In the play Othello, we see that Cassio is a man who is proud of his polite behaviour. He is a gentleman, and is interested in being thought of in that way.
One instance in which this becomes clear is in the case of his greeting of Emilia and Desdemona. When Cassio greets them, he is very affectionate. He considers this to be good manners, and the correct way to treat a lady. However, Iago uses this charm to plot against Cassio and Othello, by convincing Othello that Cassio is having an affair with Desdemona.
