The problem, it sounds to me, is with society being disrespectful towards minorities, or inconsistent in how it judges people's fashion sense. It doesn't make sense to me to blame a white girl in hoop earrings for that.
Also, it really does matter that hoop earrings date back to Sumer. How can a few bigots ruin something in a couple decades that was previously fine for thousands of years?
Also, your analogy about the paper I school is flawed. Who says the white student copied anyone? It's just as likely she was inspired by an ancient fresco of a Roman patrician as it is that she's ripping off her black friend. Maybe she wrote a paper on the same topic, and I am fine with stipulating that it was of the same quality as the other student's, but you are adding unecessary bits in order to blame the white student for what is clearly the teacher's problem.