First of all, I always thought it was "Does the Pope shit in the woods?"
It is true that belief causes 'personal' existence. But, belief doesn't cause existence in the physical world. People used to believe that the sun was a chariot crossing the sky - that doesn't make it exists. Santa Clause exists to many tens of millions of people too, it doesn't make him "real". Most people "believe" that Osama Bin Laden conducted 9/11 - that doesn't make it true.
That is a classic logical fallacy called Fallacy of the Majority or a Democratic Fallacy. Just because an overwhelming number of people believe something, doesn't make it true. An overwhelming majority of people think Ron Paul is a "kook" - that doesn't mean they are correct.
I have no problem with you or anyone else believing in magic sky-daddies, as long as it doesn't affect my life, my liberty. But, the fact that Christian Americans have destroyed my nation because of religious genocide and nationalistic empire does affect me. The US is the most religious nation on Earth, and the most anti-freedom with genocide, torture, etc....
"In the beginning of a change the patriot is a scarce man, and brave, and hated and scorned. When his cause succeeds, the timid join him, for then it costs nothing to be a patriot."--Mark Twain