What do Douglass’s observations about slaves tell us about his views on humanity in general?

My first thoughts come from Douglass' views on education. In observing and experiencing slavery, Douglass knew that ignorance serves to keep people down. Slaves were kept ignorant in order that they might also be kept subservient. Slaveowners frowned upon and prohibited teaching slaves to read and write because they believed that knowledge would cause insolence and unmanageability. Douglass' views, however, can be seen as relevant to all humanity. Education provides opportunity for everyone, whether they are slaves, share-croppers, or factory workers.

He said it's bad to be a poor man slave. To me that show cruelty.