In Alexander Dumas' "The Count of Monte Cristo," the noise in the wall gives Edmond a sense of hope. When he starts hearing the noise, he is starving himself, so he believes it is an illusion. After realizing that the noise is product of another human being, it gives him a feeling of hope and starts eating again.
The answer is that it was based on the belief that segregation was permissible as long as the facilities were equal. This is the reason why the Supreme Court’s ruling in Plessy v. Ferguson was problematic.
