I don't doubt that Kris Hadar is a very intelligent guy. So were Eliphas Levi, Paul Christian, and Aleister Crowley. Their intelligence didn't prevent them from imagining history as they wished it had happened, then writing and spreading the products of their imaginations as historical truth. Such an exercise might be philosophically satisfying, but it ain't history.
I would like to think that Hadar was misquoted, but if he really said that the Catholic Church invented the grail myth for some nefarious purpose of repression, he's simply wrong. If he actually said that the Church used the legend, or capitalized on it, for their own purposes, that would be supportable. The great antiquity of the grail legend, its pagan origin among the Celts of Britain, and its later adaptation to the literary requirements of Christian Europe, are all extremely well documented in "The Grail: The Celtic Origins of the Sacred Icon," by Jean Markale, a reputable scholar from Brittany, and in innumerable other sources.
To claim that the grail stories were "invented" out of whole cloth by anyone would reduce those remarkable legends to a banal one-dimensionality that flies in the face of their depth and richness.
Having visited Hadar's web site, and having attempted to negotiate it with both my limited French and the broken English offered by the automatic translator, it seems to me that he actually is saying that tarot originated in the twelfth century. Here again, I hope I'm reading it wrong. I would hope that he's actually saying that some of the images and concepts which were later incorporated into the tarot trumps -- wheel of fortune, devil, the virtues, etc. -- originated in the twelfth century. There's a big difference between the two. A tarot deck, after all, is twenty-one trumps, four queens, and a fool added to an Arab playing-card deck, and we know for certain that the playing card deck didn't reach Europe until the last half of the fourteenth century.
The reason I get stubborn about these kinds of things is because during the first 20 years I studied tarot, I got led down more dead-end paths than I can remember. Trying to figure out where the cards came from, what their purpose was, what they meant, I kept looking for substance and coming up with hot air. Fortunately, the canons of real history are rigid, and its requirements are unforgiving. That's because what's at issue is a little item called truth.