Of course he finds racism in writing. THAT IS HIS JOB. It was what he was hired to do. If he didn't find it,he would have to go to work for a living.
Look I am sure he has a very simple defined grading scale to match his simple mind.
Black = A
Brown = B
Asian = C
White = Pass or Fail depending on whether liberal or Conservative
Writing actually has nothing to do with his writing class.