Answer:
Because that moment shows a turning point in Douglass' life, because that situation is crucial to his decision to escape slavery.
Explanation:
As you may already know Frederick Douglass was an exceptional person and very influential in the fight for the right of black citizens and especially for their freedom.
In his book, Narrative of the Life of Frederick Douglass, he is able to tell his life story and how he managed to overcome all difficulties in being an ex-slave and building a successful path as a black man.
At an important point in this book, Douglass accurately details the struggle he had with Covey (his greatest enemy when he was a slave). Covey was ruthless and had a strong influence on Douglass's life, but during a beating session, Douglass was brave enough to fight back. This moment is told in great detail because it shows when Douglass stopped being afraid, realized that his life, health and sanity had value and decided to escape slavery.