In Macbeth, the passion is stronger than reason in that Lady Macbeth and Macbeth do not reason out their desire to kill King Duncan. They are both so passionate about becoming king and queen of Scotland until they do not weigh the consequences of their evil action. Macbeth and Lady Macbeth have their eye on the prize. They do not consider the price that will be paid for their evil desires.
In To Kill A Mockingbird, a black man will pay with his life for the community's passion to keep Maycomb a white town. Black people have no rights or justice in this sleepy town. The community is blind. There is no reasoning to their evil act of finding Tom Robinson guilty of a crime he did not commit. Because Tom is black, he is found guilty of a crime he did not commit. Reason takes a back seat in the town of Maycomb. Very few people support Tom Robinson. Atticus is the voice of reason, but he is outnumbered by twelve jurors who are prejudiced against blacks.
Passion is a very strong emotion and is responsible for many irrational choices and poor outcomes, although it is also the driving force behind many successes. It is a pity that the passion that Macbeth and Lady Macbeth exhibit in Macbeth is the destructive type. Similarly in To Kill a Mockingbird, Tom's guilty verdict and his death together with the reaction of the townsfolk towards Atticus and his children is indicative of an equally damaging mindset with passionate displays of misplaced anger and terrible injustice.
Macbeth is a decorated soldier, noble in battle and deserving of the title of Thane of Cawdor and even potentially that of king, if the witches are to be believed. At no time do the witches tell Macbeth to take matters into his own hands. In fact, when Macbeth recovers his composure, he realizes that it is his "vaulting ambition" (I.vii.27) which is responsible for his "earnest of success" (133). He reasons that Duncan is his "kinsman" and his guest. Furthermore, he is the "meek" and virtuous "subject" of Duncan. Having reasoned all of this, Macbeth resolves to let the matter go. He does not realize how persuasive his wife can be and how her accusations of cowardice will become far more offensive to Macbeth than his reasoned decision. The passion which Lady Macbeth stirs in him will be too overwhelming for him to fight against despite the chances that he has to stop himself and the visions which, rather than making him stop, stir him to even greater wrongs and ultimately make him believe he is invincible.
For Lady Macbeth, there is no contest. Her decision to remove Duncan from the picture is clear in her mind from the beginning. She reasons that it is Duncan's own folly that brings him to her home and behaves as if she is protecting her "battlements" (I.v.37) and so is justified as any good soldier is presumed to be in battle where success is measured in the "fatal" entrance of the enemy which is what Duncan represents to her. Her passion for position and for her husband's rise to be king overrides all logical thought.
In To Kill A Mockingbird, Atticus knows that the innocent Tom Robinson will be found guilty because the townsfolk of Maycomb County are too stifled in their logic to recognize the truth. There is a "caste system" (ch 13) in Maycomb and the people continue their obtuse behavior because it has always been like that there. Despite the fact that they know all about Bob Ewell's reputation and his apparent physical abuse of his daughter and even though Atticus presents compelling evidence to vindicate Tom, they still find him guilty. Atticus knows that the best he can do for Tom is to tell the truth even if Tom "might go to the chair" (ch 15). The people of Maycomb do not recognize their own hypocrisy and passionately protect what they think is right even though logic defies their beliefs. Unfortunately, they will not "see the light" (ch 15).