This one irks me just because the logic behind it is so bizarre. How is "people of color" a polite, respectful term, while "colored people" is incredibly offensive?
I saw someone on a forum I visit get jumped all over for being unable to distinguish between the terms and it was one of the strangest things I'd ever seen. People who were using "POC" every other sentence suddenly became incensed when the order of the words was innocently reversed by someone who apparently hadn't read the most current version of the SJW Handbook.