In his attempt to counter Mike Huckabee's increase in popularity in Iowa, Romney has decided to throw everything into appealing to evangelical Christians so he can save his campaign. In doing so he's positioned himself against secularists, who seem to be supported by the text of the Constitution of the United States. But he knows this plays well to the pious, so he can ride this horse 'til it collapses, because nobody's there to call him on it.
A quote from Romney's speech comes close to addressing reality:
[R]eligious tolerance would be a shallow principle, indeed, if it were reserved only for faiths with which we agree.
In the interest of completeness, I'd restate it as:
Tolerance of other worldviews would be a shallow principle, indeed, if it were reserved only for religious faiths.