How Atheists in America will Preserve Christianity

This weekend I was at a fantastic conference for women bloggers through BlogHer.  The keynote speaker the final day we were there was Indra Nooyi, the CEO of PepsiCo.  One of the things she said struck me as outrageous.  She was listing ways in which the world has changed globally.  She listed things like a shift of economic growth and power primarily from the west to include the east; a shift from women not being very important to women being a key factor in economic growth; a shift from a world where church and state were separate to a world in which they are becoming one again.  WTF? 
Now I might be misinterpreting her intent here, but all the other examples she gave were directions that showed growth and progress.  They were going from negative to positive.  So I believe she was inferring that this was positive movement.  If she wasn't inferring approval of this shift, as CEO of a global corporation, she certainly gaffed then.  However, her gaff gives me the opportunity to point out one very key thing to Christians:  eroding separation of church and state will ultimately eradicate Christianity.
Demographic shifts in population growth in the U.S. and the rest of the world put Islam as the fastest growing religion today.  In less than 50 years it will be the worlds dominant religion and I believe that in the United States that it will be the same.  Research in this area is difficult, because it is usually funded by groups with a vested interest in a certain outcome.  But nevertheless, across the board all surveys show that Islam is gaining members and Christianity is losing members.  Regardless of the timeline, it's only a matter of when. 
When this happens, the "gains" that Christians think they are getting by homogenizing religion and government and legislating according to the precepts of their religion, will be the very precedent that Islam will be able to use to enforce Sharia law at a secular level when it becomes the dominant religion.
Here's the argument: we live in a country that is based upon democratic principles and as such if we were to repeal the portion of the 1st Amendment (and even with the freaky five that are on the Supreme Court now and the asinine way they have been ruling lately I hardly doubt that would truly come to pass, but nevertheless, there are those people who would like it to be that way and I never thought they would completely rule against our political system they way they have, so anything is possible) it would mean that the religion with the most adherents would be the dominant religion.  When that religion becomes Islam, Sharia law will have the precedent it needs to become the law of the land.  Upon that happening, it would be possible for Christianity to be outlawed altogether. 
Now it's important to note that this is the worst case scenario and fairly far fetched- but then so was the collapse of our economy and the downgrading of our credit rating and both of those things have come to pass too.  When idiots like Michelle Bachmann and Rick Perry are out there displaying their Christian flag higher than their American flag, I think we have much to worry about.  And I think it's important to note that I don't mean to demean or in anyway diminish Islam.  Sharia law is fine for people who chose to adhere to it personally for themselves.  It becomes a problem when they want to impose it on others (even members of their own faith). 
Which leads me to the conclusion of my premise.  Atheists, agnostics, skeptics and apathists like myself, are the ones who are best suited to keep that precedent from occurring.  By not adhering to any religious belief we are the ones who will be best suited to make sure that all religions are treated equally.  We are the ones who will protect all religions equally.  By allowing those who are free from religion to legislate, we are really protecting those who most benefit from freedom of religion.