That was just a poster joking and speculationg how the Obama campaign would explain it all away.
From the research and reading I've done on the origination and massaging of this rumor, the "why'd he" explanation first came from somebody at Kos.
I find the interest in "who found it" and "who's withholding it" to be fascinating. Objective people like to get accurate raw information, regardless of the motives or affiliations of the sources.
Read this: Obama interview transcript - 2004. It's Obama in Obama's words. He claims to be a "mainstream Christian," and explains what that means to him.