It was this "Paradox" which fueled the Civil Rights Movement - especially after WWII. African Americans fought against fascism and racism abroad, only to come home to experience racism which never went away here. Americans of Japanese descent helped free Jews from concentration camps, while their own families were being held in detention camps at home. World War II highlighted the disconnect between the ideals and reality of the USA, in a way which could no longer be ignored.

https://medium.com/engendered/before-brown-there-was-james-f132104f9766