Iago's Animal Motif

In William Shakespeare’s Othello, the characters (Iago in particular) often refer to other characters or concepts as animals, creating what I believe to be a motif. On line 108 of the play, Iago, having already displayed his disliking for Othello, refers to him as a “Barbary horse,” informing Brabantio that his “nephews [will] neigh to [him]” (558). Here, Iago is trying to explain to Brabantio that Othello has stolen his daughter, which could result in animalistic grandsons. In advance, he informs him that his “daughter and the Moor are making the beast with two backs” (559), a way of saying the two are engaging in a sexual relationship. Early on in the play, Iago has already used animals to make people or situations seem worse than they might be. Furthermore, when Roderigo mentions his thoughts of suicide, Iago says if he were to do the same “for the love of a guinea-hen, [he] would change [his] humanity with a baboon” (571). Once again, Iago uses animals to refer to people in a somewhat insulting way in order to prove his point. He proceeds to tell Roderigo that drowning is for “cats and blind puppies” (572). Iago’s continuous use of animals creates a motif in my opinion because it is a recurring theme throughout the play. In addition to the usage, I find it interesting that the motif is typically used as an insulting or downgrading substitute; however, it makes sense in context because Iago normally uses it to prove a point. A few questions about the text so far: Why is Othello accused of witchcraft or magic when making Desdemona fall in love with him? This seems to be a recurring theme lately. Is there some sort of religious connection like in Dr. Faustus? Or is Brabantio just very far in denial of the relationship?