I think because they had to leave their home and even though they might be somewhere better it just doesn't feel right to them like its just not where belong or should be.
Hope it helps not sure if right
He believes that middle and upper class black Americans are primarily interested in effacing their history, background and culture and want to copy white people and for example as poets be like white poets and men like doctors.,lawyers etc are often marrying lighter skinned women than themselves.
The meaning of the word incredulous, based on its parts is: "full of disbelief".
The prefix in- is one of the many prefixes that mean "no". So it denies the meaning of the word following it. One example would be the word inefficient. By adding the prefix in- to the adjective efficient, we deny the adjective. If we call a person inefficient, we are saying the person is "not efficient", not able to finish tasks in a proper time and manner.
As for the other part of the word we're analyzing here, "credulous" comes from the Latin word "credere", which means "believe". A credulous person is a person who believes in things easily, without questioning or reasoning.
By putting in- and credulous together, we form "incredulous", or "not credulous". So an incredulous person is a person who does not believe easily - who is full of disbelief.