Many white people wonder why there is a difference between when Afro-Americans and whites can use the n-word.
The reason is called desensitization.
When Blacks use that word they are practicing a social mechanism for protecting their group.
At one time in the past, and still continuing today, how a black person responded to the n-word could be a matter of life or death. As a protective mechanism, black people would use that word in their group so that they would learn not respond to that word automatically.
So whites cannot use the n-word to blacks until it has lost all its meanings in our society as an insult.