I don't know, these days I think people are more scared of Muslims than they are of blacks.
Imagine, though, the backlash that would've been created if the rumors of Obama's religion were that he was a secret Jew.
I would've found it even more funny if those were the rumors, but the Jewish community would be up in arms. Maybe, though, because the Muslim community in the US is less than 1%, but my point is valid.