"unlike Islamic scholars, a true 'scholar' studies more than one book"
Some jokes seek to contrast literal truth with a deeper obvious falseness, while others seek to contrast obvious literal falseness with a deeper truth. That joke is intended, I think, to be of the second kind: obvious literal falseness contrasting with a deeper truth.
That said, from what I know of Dawkins, he tends to be quite abrasive. He sometimes manages to get even atheists mad at him.