Because the book was about his time posing as a black man and finding out what black people "like him" were treated like.

A line from Langston Hughes' poetry (the last line of "Dream Variations")

Only someone who never read a single sentence of that book would feel the need to ask such a question.

I am guessing you have neither watched the movie or read the book

To inform

Maybe you should read the book and find out.

Because blacks like him?