Sentence:  ... they know that the low social level of the mass of the race is responsible for much discrimination against it, but they also know, and the nation knows, that relentless color-prejudice is more often a cause than a result of the Negro's degradation; they seek the abatement of this <WSD>relic</WSD> of barbarism, and not its systematic encouragement and pampering by all agencies of social power from the Associated Press to the Church of Christ. 
Meaning of the word marked with <WSD> tags:  That which remains; that which is left after loss or decay; a remaining portion.