'useful' -- I agree.

I have always contended that the Soviet Union/Stalin weren't atheist, just using the "opiate of the masses".

I liked the book. To show how dumb some of the religious are I mentioned to a co-worker that I hated life celebrations or funerals where people claim the dead are with friends now talking, etc., etc. My coworker friend replied that some people are more spiritual than others. People like this need free copies of the Dawkins book.

Why only there?

I think that the above is attributed to Lucius Annaeus Seneca, a stoic philosopher. Of course, any popular, widely held belief may be considered useful by rulers.