That's fair, but I'm not sure that making movies for a global audience means a global audience needs to be represented by proxy on screen beyond reason. Exodus? That was a ****ing travesty in terms of accuracy as well as representation. But if you're making a global movie based on certain source material I don't see why it needs to be changed?
No movie will ever represent everyone and don't believe anyone outside of those deranged SJW on Tumblr believe they should.
White is the default race in a lot of literature like long established comics that were created in the early 20th century time period. I don't think you need to race swap everyone but some roles can be open to being played by different races without losing the essence of the character.
Many of the roles Will Smith has played in his are where written as white men. Deadshot or Perry White being black doesn't change anything fundamental about their characters.
If every role was kept to how they were in the original source material then movies would be a lot less diverse and many talented non-white actors would not get much work.
You are right, to an extent. It is a fantasy movie, in a sense that there are fantastic being, characters and occurrences, but it's set in the actual real world place (for most part) and within the boundaries of an actual culture. Arthurian myths were always historically true when it comes to the cultural aspect. Now, I don't think they'll claim that Bedivere is an Anglo-Saxon or anything of a kind, but he is still a black person with a French name and title of a knight in medieval Britain. Pretty nonsensical in my opinion.
The Arthurian myths have been constantly changing over the centuries. The Merlin figure didn't merge with the Arthur legend until Geoffrey of Monmouth's pseudohistorical Mediaeval 'The History of the Kings of Britain' which is not in anyway historically accurate.
There is no canonical version of the Arthurian legend.
A black person with a a French sounding name in Medieval Britain isn't really that much of a stretch. Medieval Britain had traders, merchants, mercenaries and so on form other parts the world. We know for a fact that there was some north Africans in Roman Britain. I don't think anyone could say for a fact that there has never been a black person in Medieval who had a francophone name.
Bedivere was Arthur's marshal.
One of the most famous knights in European history was William Marshall who rose from obscurity due to his courage and skill as a knight, and he served four kings, ultimately becoming one of the most powerful men in Europe.