The most likely reason why Emerson included this quote in his speech is that Emerson wanted to highlight the hypocrisy of society, and its treatment of John Brown. He wants to motivate people to think about the injustice of their condemnation of John Brown. Emerson argues that Brown was so persecuted because he decided to defend the interests of the poor. He argues that if Brown had instead defended the interests of the rich, he would not have gotten in trouble, as it is usually the rich who make decisions on morality and righteousness.