How can one deny the supernatural associated with religions other than their own?

Imagine the following story:

• I was in my room one night.
• Suddenly, my room became exceedingly bright.
• Next thing I know there is an angel in my room.
• He tells me an amazing story.
• He says that there is a set of ancient golden plates buried in the side of a hill in New York.
• On them are the books of a lost race of Jewish people who inhabited North America.
• These plates bear inscriptions in the foreign language of these people.
• Eventually the angel leads me to the plates and lets me take them home.
• Even though the plates are in a foreign language, the angel helps me to decipher and translate them.
• Then the plates are taken up into heaven, never to be seen again.
• I have the book that I translated from the plates. It tells of amazing things -- an entire civilization of Jewish people living here in the United States 2,000 years ago.
• And the resurrected Jesus came and visited these people!
• I also showed the golden plates to a number of real people who are my eye witnesses, and I have their signed attestations that they did, in fact, see and touch the plates before the plates were taken up into heaven.

This is the story told by Joseph Smith, the creator of The Book of Mormon. Many people would read this story as a fairy tale as that is what it most aptly resembles, but Mormonism is one of the fastest growing religions on the planet. No one outside of little kids believes in Santa. No one outside the Mormon church believes Joseph Smith's story. No one outside the Christian faith believes in Jesus' divinity, miracles, resurrection, etc. Your rational mind knows with certainty, yet 4 billion others believe in something different with that same certainty. 
http://www.talkorigins.org/origins/faqs-evolution.html