What was the struggle for civil rights more difficult because of the " separate but equal " doctrine established in the plessy vs ferguson case?

The struggle for civil rights became difficult with the separate but equal decision when it was used by the supreme court which tells it does not affect the civil rights of the African Americans stated in the 13th and 14th amendment. At the Louisiana Railroad Plessy argued that it was his right under the Separation Car Act to sit in at the white's car when he was asked to sit on a black car. The state classified him as black because of his part descendancy from a black race. 

Because the discoveries were some of the oldest human remains.