Well, back in the 'unenlightened' days, we studied the races that way. Now, we have to have the government and lots of people educated beyond their intelligence to tell us we can no longer use those words, they hurt someone feelings. Horsefeathers!! It is just a way to attempt to control not only the speech of Americans but their very thoughts. Anyone who buys into the racist, bigot screed is just aiding and abetting the people who would like to keep us divided.
Had the teacher done anything in the past to that child? I doubt it. But you know in this society - words matter more than anything else. It doesn't matter what a person feels or how he acts, if only he says the right things.
Just get over it!! If that is the worse that child has to live with in his lifetime, he will be lucky indeed.