Put it this way. Poet Robert Graves, in his generally sympathetic introduction to a translation of the Morte D'Arthur pointed out a reason for his popularity beyond Wales may have been that he rode a horse and hated the Saxons. Now the Plantagenets, who ruled that part of England and France where he became popular, were Normans who had conquered Saxons and rode horses. They picked up the tales, apparently, from the Bretons, who were basically Celts who had fled Britain with the Saxon Invasion -- in other words, though this oversimplifies, displaced Welshmen.
Anyhow since Plantagenet times Arthur and his Knights have been held up as exemplars of how the ruling class should behave. This was in fact the whole nature of the stories until Tennyson's Idylls of the King, which was both a continuation of it in modern times and a transition to modern views of him.
The character has been revised, thoroughly, many times since his days as a folk hero for the welsh as this old poem will show:
http://www.lib.rochester.edu/camelot/annwn.htm
reconciling THAT Arthur with the one in Sir Thomas Mallory or Wolfram Von Eschenbach even would be very difficult and Marion Zimmer Bradley or Mary Stewart? Hah.
In a very real sense people are saying openly what many people have felt throughout modern history, and Monty Python and the Holy Grail essentially appeared at a moment where the British could face class resentments in ALL their myths. As the Harry Potter books show, class distinctions are alive and well in Britain, and you have to understand Arthur and Robin Hood as opposite exemplars -- Arthur is about the justice of the Ruling Class while Robin Hood is about the defense of the realm from its corruption.
There is not much left of Arthur in ANY conventional tales. For more than a thousand years he has been the vehicle for the propaganda of the ruling classes. Remember that.