You don't have to agree with the "exclusivity" of that statement, but what he said is most certainly true. While others were "tolerated"* in their decision not to be Christian, it was expected by its founders and framers that America would most certainly continue to be a Christian nation and be governed by Christians. A thorough reading of the founding documents, writings of the founders and a knowledge of the kind of men they were will reveal insight as to the kind of government they meant for us to have and it was not based on "diversity". Embracing "diversity" is what caused the downfall of Rome and Greece and it's where we're headed if we don't take America back to her roots of one nation under God.
*Note that I use tolerance in the traditional meaning - to accept, to allow; I do not use it in the new politically correct meaning - to embrance and adopt.
>it was expected by its founders and framers that America would most certainly continue to be a Christian nation and be governed by Christians
I respectfully disagree. Writings by the Framers indicates they were wary of mixing Church and State, having learned that lesson from the bitter wars in Europe between Protestants and Catholics. If the Framers were so adamant about Christian rule, wouldn't they have made their intentions clear in the Constitution? Diversity is destabilizing to the effect that liberals encourage us to emphasize our differences rather than the commonality between our religions and cultures. The melting pot works because we have differences but are willing to "melt" and celebrate our common values and pride in being American.