When you think about how fantastically successful the Jewish lobby has been, though, in fact, they are less numerous I am told - religious Jews anyway - than atheists and [yet they] more or less monopolise American foreign policy as far as many people can see. [emphases mine.]
The highlighted phrases illustrate Dawkins' use of the heuristic of social proof - he seems to believe Jews are small but monopolize US foreign policy because others tell him so.
But you could use exactly the same method to believe in God - or at least to be agnostic. God exists as far as many people can see - indeed, many more, for much longer, than believe in Jews' influence on foreign policy.
So, why is Dawkins happy to use social proof in one context, but reject it so violently in another?
It would be too glib to say this is an example of how rational people cease to be rational in thinking about politics, because there's something to be said sometimes for the use of social proof.