To add to the point in the above post about Douglass's purpose to inspire people against the nature of slavery, Douglass also uses exaggerated moments to influence his audience. For example, while in Baltimore, Douglass claims that he makes a grand apostrophe to the passing ships in the harbor. In the apostrophe, he says that he cried out to the ships asking why they were free while he was kept in bondage. The apostrophe is quite emotional and breaks the more objective tone developed previously in the narrative. One assumes that Douglass did not actually orally address the passing ships in the harbor--surely a slave seen engaging in such behavior would be cause for the authorities to inflict punishment; however, Douglass may very well have had these thoughts and simply presented them in such an exaggerated manner to influence his reading audience.
I suppose in the final analysis that Douglass value of expanding the moral and ethical imagination of the reader is something that transcends the notion of exaggeration of self- glorifying. His narrative is written at a time where people did not know or did not care to know about the nature of slavery. The language and tone used in the work is meant to provoke individuals into action and meant to inspire individuals against the nature of enslavement. It is going to be difficult to label any portion of the text as self- glorifying because of Douglass own experience as a slave, his connection to America's "original sin."