It's just Dawkins' opinion. And, as we all know, opinions are like posterior exits to the human alimentary canal, everyone has one.
Dawkins apparently has a bigger opening than most...more excrement...
True, it's just his opinion, but after reading his proposals for the eradication of traditional religions, I'm inclined to believe that he wishes his opinion were fact.
Given the nature of facism and communism in the 20th century, that makes me take his opinion very seriously...