In one aspect, Shakespeare constructs the absence of the representation of racism. When the Duke judges in Othello's favor regarding Desdemona, he does so irrespective of Othello's race since he knows that a man is honorable for his beliefs and actions rather than for his race.
Shakespeare shows that racism is a resort of the desperate and the ignorant.
Brabantio, Desdemona's father had welcomed Othello into his home - 'oft invited him' in fact, to share his dramatic stories. He turns against the Moor once he elopes with Desdemona. It is this deception which provokes Brabantio's racist reaction: he is merely reacting to the loss of his daughter's innocence. Racist comments are therefore seen as the low blow of the distressed and anxious father, ignorant of his daughter's passion and desire.
We see Roderigo refer to Othello as 'thick lips' and then later see how Roderigo is used by his 'friend': a gullible and weak 'fool' who is Iago's 'purse'.