I chose answer C before reading the next paragraph.
The real sin of this professor was her arrogance, which prevented her from hearing new evidence that contradicted what she had read in the past. You were absolutely right to present better evidence and to stand by it. A professor who cannot stand to have her ideas challenged has no place in any college or university.
I see nothing in the piece that tells me that race had anything to do with the professor’s poor responses, though. She just had a very closed mind.