Iago's tactics

Regarding the moments Iago makes use of various tactics to manipulate different characters; I agree his main technique is to use people’s virtue against them. It can be explained in the following with examples of Iago deceiving Roderigo, Cassio and Desdemona.
Firstly, Iago has manipulated Roderigo based on their mutual trust and Roderigo’s faithful affection towards Desdemona. In act I scene 3, Iago manipulated Roderigo’s trust and brainwashing him to give his money to him, which seemed to be a rational thing to do for his own good. When Roderigo asked Iago ‘Wilt thou be fast to my hopes, if I depend on the issue?’ Iago responded by saying ‘Thou art sure of me. Go, make money.’ This directly indicated that Iago manipulated Roderigo’s reliance and belief in him. Repetition of ‘put money in thy purse’ also intensified Roderigo sense of righteousness in following Iago’s advice. From ‘I hate the Moor. My cause is hearted; thine hath no less reason. Let us be conjunctive in our revenge against him.’ Iago duped Roderigo to his plan by exemplifying their common enemy, Othello. This technique was used based on their manipulating their friendship, which seemingly illustrates that Iago was a helpful and supportive friend who will assist Roderigo to eliminate their common enemy.
Furthermore, in Act II scene1, Iago lured Roderigo into his plan by speaking like an adviser who guided him to the right decision for his own good. He strongly emphasized that Desdemona will leave Othello soon and fall into Cassio, suggesting that Roderigo should follow his plan to remove their common enemy, Cassio. Iago acted as if he could foresee the future by illustrating an imagery of Desdemona’s affair. ‘Mark me with what violence she love him still for prating? Let not thy discreet heart think it.’ Iago suggested that Desdemona’s impulsiveness in getting together with Othello has proven that she will leave him one day when their affection is over. By showing this, he altered Roderigo’s virtue of love and faith towards Desdemona into jealousy towards Cassio. The line ‘Now, sir, this granted-as it is a most pregnant and unforced position.’ Iago spoke in a provoking tone, duped Roderigo to believe that he’s telling the truth which is a natural and obvious interpretation of Desdemona and Cassios’ relationship development. ‘I cannot believe that in her; she’s full of most blessed condition.’ As Desdemona in his perception, was a goddess with paragon of feminine virtues, Roderigo refuses to believe in his trusted friend Iago at first. However, Iago further goaded him with sly storytelling. ‘Didst thou not see her paddle with the palm of his hand? Didst not mark that?’ Iago convinces Roderigo to agree that Cassio’s seemingly innocent greeting had a lecherous undercurrent. To sum up, Iago altered Roderigo’s pure admiration and love towards Desdemona, into jealousy and hatred towards Cassio.
Also, in Act II scene 3, Iago has manipulated Cassio’s pure admiration of Desdemona to put forth his plan. The lines ‘He hath not yet made wanton the night with her, and she is sport of Jove.’ and ‘what an eye she has! Methinks it sounds a parley to provocation.’ Iago painted the admirable divine Desdemona as a wanton woman. By associating with Greek mythology, he illustrates Desdemona to be a wild and notorious womanizer who’s Jove’s consort. In responds, out of pure admiration and conscience, Cassio raised so to defend Desdemona. However, Iago altered his defense for admirer into lustful intention towards Desdemona. He manipulated these pure admiration virtues and misled others to believe that Cassio has intention to develop sexual relationship with Desdemona.
Moreover, Iago manipulated Cassio’s respect and trust in him to trick him to join him a toast. ‘O, they are our friends. But one cup! I’ll drink for you.’ Iago tempted Cassio to consume alcohol by pretending to be a friend. Noticing that Cassio respected Othello, Iago manipulated his virtuous respect and loyalty to trick him in drinking wine. The lines ‘to the health of black Othello’, ‘to the health of our general!’ indicates Iago cunning techniques in manipulating Cassio’s loyalty in his general which ironically brought him to the brink of his decline.
In addition, Iago indirectly manipulated Desdemona’s sympathy in creating the illusion of Cassio and Desdemona’s affair to put fourth his plan. In Act II scene 3, ‘So will I turn her vitue into pitch, and out of her own goodness make her net that shall emesh them all.’ Iago directly claimed that he would twist the virtue of Desdemona. Also by suggesting a net imagery, he firmly suggested his determination to trick Desdemona, Othello and Cassio. Desdemona, the woman with a paragon of feminine virtue, with kind nature and willingness to help; also, a woman that Othello depends deeply on as we can seen from the line ‘That she may make, unmake, do what she list, even as appetite shall play the god with his weal function.’, Repetition of ‘make, unmake’ reinforce that Othello is easily influenced by Desdemona. Iago, knowing the virtue of Desdemona, has exploited them and used her as an extended tool to convince Othello into believing she has an affair with Cassio. Further proof was founded in Act III scene 3; we can see that Iago manipulated Desdemona’s sympathetic heart from the line ‘Assure thee, if I do vow a friendship, I’ll perform it. My lord shall never rest: I’ll watch him tame and talk him out of patience.’ Iago’s cunning way of manipulation based on people’s virtue was again presented.
To conclude, I agree that Iago’s main technique is to use of people’s virtues against them, which in the above, the ways he dupes and goads Roderigo, Cassio, and Desdemona into his traps have significantly illustrated his technique.