Indeed it seems to be a broadening of the term, as you have so elaborately explicated. I guess I just see it as problematic when the broadening involves such a leap. As you say, it's hard to argue for a 12-year-old race. I know that linguistics works descriptively instead of prescriptively, so I can see your desire to, aside from saving the OP some embarrassment, analyze the origin of such a misuse. However, it seems to me that this sort of misuse should be pointed out to the misuser so that he may avoid it in the future, and thereby give the impression that he is at least somewhat educated.
Having said all of that, I definitely understand where you're coming from, both from the emotional side and the linguistic analytical side, in your breakdown of this situation. Believe me, if I believed it were truly a metaphor for discrimination in general, I wouldn't have brought it up. However, one thing that bothers me about common language usage is that people don't understand the words that they use. I suppose I should give more leeway, as I sometimes misuse words due to not completely understanding what they mean, but at the same time I think there should be some standard (which is probably only arbitrarily decided by me, and desired to be understood by all, as if it could). I'm sure we could argue this to death if we so desired, but in lieu of that (at least for now), I'll just say that I have much more tolerance for words being misused by people who understand that they're misusing them and misuse them as a joke than I do for people who misuse words out of ingorance. Yes, I realize that this opens up a whole new argument, but I'll leave it at this for now. :relief:
