I attended an in-service course for teachers, run by two gentlemen of Afro-Caribbean descent, in Sheffield back in the late 1980s. When I asked the course leaders for an acceptable term to use collectively for all people who were not descended exclusively from many generations of white parentage, I was told that the only acceptable word was 'black'. I asked whether this applied to those 'of mixed race' and I was told forcefully that I must refer to them as 'black'. I pointed out that I required a term which also included people of Asian descent (including those from both India and China). Once again, I was told (very forcefully) that I should only refer to them as 'black'!
I mentioned this to one of my pupils, whose family ran the local Chinese takeaway. Her reply expressed my own feelings perfectly, even though it used a few words which wouldn't normally have been acceptable in my classroom ;-)
Sometimes simply using the definite article can change the perceived meaning of a word. One of my extremely able (and usually articulate) 6th form students said 'I stay away from Firth Park. It's full of blacks. I can't stand them'. This apparently racist comment came as a shock to me as the student who uttered it was of African descent, with the darkest skin possible. When I asked her about it she explained "I might be black but I'm not a black".
Chris