Ahh - we have different sources for the same context. For anyone who has not read Russell's "Why I don't believe in God", get it - it is in his classic, quality, writing style.
Eric Boyd wrote:
> Dan Plante <firstname.lastname@example.org> writes:
> I'm rather partial to the quote that was posted a while back (I don't
> remember who posted it); it went something like "....so when you
> understand why you don't believe in all those other gods, you'll
> understand why I don't believe in yours.", or words to that effect.
> It's wide spread on the 'net. I know I've posted it here a few times;
> this is the version I have:
> "When you understand why you reject the 9,999 other gods you
> will understand why I reject all 10,000." - unknown
> Unfortunatly, this quote is tailored to monotheism -- which is really
> more specific then I like to get.