The first protected right in the Bill of Rights is religion. Why, out of all of the rights the founders could name, would they pick the freedom of religion to stand next to free speech and the free press? What does religion have to do with preserving the United States?
Most of my students usually think the First Amendment clause about religion creates a separation of church and state. They are surprised, when they actually read the amendment in my class, to find out that it says no such thing. In fact, it says: "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof...." When my students refer to the idea of the separation of church and state, they merely echo the thoughts of modern liberalism, which interprets the first clause of the amendment, while ignoring the second clause altogether.
The founders knew that giving the government the authority of religion was dangerous, and would always be abused. They also knew that to mix religion and politics would corrupt religion and its intent. Hence, the US should have no state church, but it also must keep government from interfering with the free exercise of religion, except where religion becomes destructive to other rights (such as blowing people up in the name of Allah.)
But the key here is that we must protect, and continue to protect, religion in the US in order to maintain a moral system that is different from the state. Let me repeat that. We must protect religion in order to maintain a moral system that is different from the state.
This is an important concept to remember. When Stalin took over communist Russia after the death of Lenin, one of the first things he did as the new dictator, was to kill as many priests as he could find, and to destroy the churches. Why did he do that? Because he knew that in order to control the people (i.e., to kill them and to enslave them), he could not allow a competing moral system to remain. Morality, according to Stalin, must remain the property of the state. (And by state, Stalin really meant himself.)
This is how dictatorships develop, when the state takes on the responsibility of defining morality for all of its citizens. There can be no dictatorship unless it is upheld by corrupted religion (such as France's totalitarian monarchies), or unless it is upheld by a wholly false religion (such as Hitler's parody of religion in his blood flag ritual), or unless it replaces religion with its own morality (such as all communist dictators have done).
You nor I may like a particular religion, or particular religious beliefs of certain individuals, but we must protect the free exercise of religion in this country if, for no other reason, than to prevent the state from dictating what is right and what is wrong. When the state defines morality, we, as people of a free society, will cease to be free.