What is the purpose of douglass describing the better treatment of the city slaves compared to the plantation slaves in the narrative of the life of frederick douglass?

How does this quotation add credibility to freedman'sstatement that the immigrant voyages were not pleasant? read edward corsi's quotation from the book immigrantkids by russell freedman. edward corsi, who later became united statescommissioner of immigration, was a ten-year-old italianimmigrant when he sailed into new york harbor in 1907: the officers of the ship went striding up and downthe decks shouting orders and directions and drivingthe immigrants before them. scowling and gesturing, they pushed and pulled the passengers, herding usinto separate groups as though we were animals. afew moments later we came to our dock, and thelong journey was over. o it is from an actual immigrant who experienced roughtreatment by the ship's workers. it is from an actual sailor who herded the immigrants likeanimals on the decks. it is from an actual writer who wrote about a fictionalfamily immigrating to the united states. it is from an actual historian who studied the immigrationexperience at ellis island.