At the inn where Othello is lodging, Iago tells Othello that he wanted to stab Roderigo when he hears the things Roderigo was saying about Othello. He also warns Othello that Brabantio is likely to try to legally force a divorce between Othello and Desdemona. Othello seems unconcerned.
Iago changes sides seamlessly. He tries to provoke Othello by suggesting that Roderigo has slighted his manly honor. But, at this point, Othello seems completely secure in himself, immune to challenges to his manhood.
Just then, they see a group of men approaching. Iago says it must be Brabantio and advises Othello to go inside. Othello refuses, preferring to face them, saying he has dutifully served the state of Venice and his conscience is clean: he loves Desdemona.
Othello knows that his honorable military service will outweigh Brabantio's grievance. He's also the first character to speak of love. All the other men seem to think of women as something to possess, not love.
The men turn out to be Cassio and servants of the Duke of Venice, sent to bring Othello to meet with the Duke regarding an urgent military issue in Cyprus (an island protectorate of Venice).
Cassio's news is proof that the state's need for Othello's military leadership will outweigh any racial prejudice against him.
Iago then mentions to Cassio that Othello has married. But before he can say who Othello has wed, Roderigo along with Brabantio and his men arrive. Brabantio states that Othello must have enchanted Desdemona, or else why would she have gone "to the sooty bosom of such a thing as thou" (1.2.70-71). He orders his men to seize Othello.
Brabantio gives full voice to his injured sense of manhood by interweaving the language of racial prejudice with horror at interracial sexuality. He cannot believe that things are as they seem: that his daughter has voluntarily eloped with a "sooty...thing."
Othello is unfazed, tells everyone on both sides to put up their arms, and informs Brabantio that he has been called to meet with the Duke on state business. Brabantio decides to accompany Othello to the Duke and air his grievance there.
Agreeing to go before the Duke's court of law, Othello remains confident that his honorable service will outweigh his outsider status.