In The Invisible Man, why does Dr. Bledsoe expel the narrator from college?

Dr. Bledsoe, as the principal of the narrator's college,
of course has the power to expel the narrator. However, what triggers this expulsion is
when the narrator takes Mr. Norton, an important guest of the college, to the slave
quarters and to the Golden Day, even though the narrator was asked by Mr. Norton himself
to take him there. In rather a shocking speech, Dr. Bledsoe calls the narrator an
insulting word used to denigrate blacks, and then expells him, simultaneously slamming
down a shackle on his desk to emphasise his words. For Dr. Bledsoe, a black man himself,
to act in this way reinforces the way that racism and oppression does not only occur
between different ethnic groupings but also within ethnic groupings. In spite of the
obvious unfairness and injustice of this action, forgetting the insulting nature of it
for one moment, the narrator is told very clearly that he has no other option but to
accept his expulsion and leave.