Well, Othello was a bit of an outsider. He was not originally from Venice, he did not come from a well-known or important or rich family, and his skin was a funny colour. Although he might be a fine fellow in his own right, he is not the kind of person that a Venetian aristocrat like Brabantio would pick as a husband for his daughter. What is more, he did not ask Brabantio first before discussing marriage with Desdemona.
Brabantio warns Othello that if his daughter, Desdemona, deceived him in order to marry Othello, then she can just as easily deceive Othello.
Roderigo is hoping to gain Brabantio's favour so Brabantio will support Roderigo's bid to marry Desdemona. Unfortunately for him, 1) Brabantio doesn't like him, 2) Desdemona doesn't like him, and 3) Desdemona is already married to Othello.
Brabantio accuses Othello of making off with his daughter Desdemona and marrying her against her will, in effect raping her. However, it soon becomes apparent that Desdemona had freely consented to marry Othello and was not under the influence of a drug or other mysterious mind-altering substance.
Roderigo had previously asked to marry Desdemona, but neither she nor Brabantio was impressed by the idea.
Brabantio did not want Othello for a son-in-law. Despite his appearance of being nice to Othello, Brabantio is a racist man. He accused Othello of "witchcraft" and stealing his daughter because he cannot understand why Desdemona could possibly love a black man.Furthermore, at the beginning of the play, he tells Roderigo to go away because "My daughter is not for thee". However, when he learns that Desdemona had indeed eloped, he wishes that it was Roderigo who had married Desdemona instead.
Brabantio disapproves of Othello and the relationship he has with Brabantio's daughter Desdemona. This is not because Othello is not worthy of Desdemona because he is a much respected officer, but because he is a Moor (in that time an African) and therefore considered beneath the Italian people.
Barbantio's reaction to Othello and Desdemona's marriage was he thought that Othello used magic on Desdemona. He couldn't believe his daughter, a Venetian woman would love a dark Moor without Othello using magic.
Iago, Brabantio and Roderigo. Nobody else seems to care. And probably Brabantio is the most intolerant--he will have Othello over to supper but he wouldn't want him to marry his daughter. Roderigo wouldn't care except that they are rivals for Desdemona and Roderigo will throw any dirt that might possibly stick at Othello. Iago's position is mysterious, but whatever his motive for disliking Othello (and who knows, race might be a part of that), he is sure prepared to make an issue of Othello's race around the racist Brabantio.
Brabantio thought that Othello had used magic to get Desdemona to marry him. This was based on the highly racist assumptions that a) Othello was so ugly that no woman could possibly love him without some love potion, and b) Othello was from some weird foreign background where people probably used love potions all the time.
Desdemona marries Othello at the beginning of the play against her father's will. The two secretly marry.
Othello insists the men put away their swords (1). He defends himself in his marriage to Desdemona (2). He demands Desdemona be brought to him (3). He insists arrangements be made for his wife to be made comfortable (4). He sends his ensign to accompany his wife (5).
roderigo is jealous of othello because desdemona has chosen othello asher suiter despite the overwhelming offers roderigo has made and the racial difference in othello, which at that time would be considered taboo. so desdemona would rather go against society with othello than be with roderigo.