Technically speaking, this is the opposite - the point is that while a prescriptivist would find the whole thing a bit silly a descriptivist would have a problem with this situation, because it is creating new racial insult (eg, calling something a blacklist in the presence of a black person) where none existed before.
It seems like a mistake to invent racial terms out of whole cloth for no reason. It shouldn't be done.
Linguistic prescription is saying it shouldn't be done because there are rules, and the change breaks them.
I'm not saying that. My position is it shouldn't be done because creating new slurs for no reason is stupid. A prescriptivist and a descriptivist could both agree to that, though they'd disagree with each other on whether the idea of the change is legitimate.
Which is probably a similar position to ccmcarey's original comment. No position was taken on whether the change breaks the rules of language or not, the argument was that either way the change is being bought on by ignorance of both normal usage and the lineage of the word (ie, potentially in defiance of both prescriptivist and descriptivist logic).
This isn't really an issue of prescriptive vs descriptive philosophy. Although the descriptivists will be hopping mad.
It seems like a mistake to invent racial terms out of whole cloth for no reason. It shouldn't be done.