The author cites this claim from an article written in 1964 by historian C. Vann Woodward.
You're off to a terrific start! Since I mentioned the Jim Crow Laws and the Plessey vs. Ferguson case in my first RefAnnBib comment, I'm not sure if my suggestions influenced you to speak about them, but these two things are very concrete examples of how black people were degraded, and they serve to show how blacks were treated inhumanly. It's a good idea to include a piece by C. Vann Wood since it lends credibility to your argument because he witnessed these events firsthand(primary source) and saw the impact these stipulations and court ruling had on blacks and other minorities. He personally witnessed how the African population was plagued with feelings of sadness and despair as a result of these things. If you haven't already, go back and read my first comment because I believe it's very insightful and will hopefully enrage a flame within.