A few days ago I came across this article online which quoted George R. R. Martin invoking the medievalism of his books to explain why there are few major characters of colour either in them, or the TV series. It quotes Martin's Livejournal, where he responds to a reader's question about the absence of Asian characters in A Song of Ice and Fire: "Well, Westeros is the fantasy analogue of the British Isles in its world, so it is a long long way from the Asia analogue. There weren’t a lot of Asians in Yorkish England either." It's a response that directly parallels comments made places like the fan site westeros.org which I wrote about in an article that went online last week here.* It's hard to argue directly with that kind of statement; taken by itself it's factually true. But it also masks the fact that the Middle Ages, even within Europe, were culturally, lingustically, and racially diverse.
* visit our Facebook page for a link to a free download if you don't have access to the journal Continuum through a university library