It is a quote made when slavery was there is the United States, when most of the people tried to discriminate people on the basis of their race.
If you're asking in Grammatical aspect, then there is nothing complex in this sentence, just means, that if you are black that it's a bad thing [ just by this quote ]
The author of a book wants to make the reader feel what the topic of book is about. for example if the book is sad, the author wants the reader to feel those emotions.
