because it's telling the same story of <em>My Lord Bag of Rice</em> just paraphrased, which means express the meaning of (the writer or speaker or something written or spoken) using different words, especially to achieve greater clarity. ((yes i used google to find the definition of paraphrased lol))
Atticus is fighting a case case for Tom Robbinson the so called 'mockingbird' he is speaking of is Tom and it is a sin to kill an innocent man as Tom did not r'pe Mayella Ewell.