One of the white teachers at my middle school (which was in a black neighborhood) admitted that she never knew what to say because she didn't want to risk accidentally saying something that would have been seen as politically incorrect, and I have noticed myself over the years that those two terms in particular seem to bounce back and forth between being P.C. and un-P.C. From what I understand, "African-American" is un-P.C. right now because you can't alway assume somebody who is black is automatically of African descent, and that actually does make sense. It's kind of like how Donald Trump can't seem to grasp that just because someone is an American citizen, that doesn't necessarily mean they automatically celebrate Christmas, which is why it is P.C. to say, "Happy Holidays," instead of, "Merry Christmas."