Actually, Brown's interested in making a ton of money. He knew an attack on Christianity would be greeted enthusiastically by the "beautiful people", while an attack on Islam would not only get him dis-invited to the right cocktail parties, it would get him targeted for a Jihad. So he attacks a faith he can attack safely and with a good profit margin, while maintaining his PC credentials with the fine wine & limousine crowd.
Yeah, you're right. It is a BIG thing. I saw the other day, Google had something about it on a fairly plain search page, and at Barnes & Noble, they've gone all out (at least at my neighborhood's branch).