The importance of church-state separation for the religious

This is really so obvious that I don't see why it is not more widely acknowledged:

The much-celebrated freedom that is the ground of the American consensus is, above all, freedom of mind and heart; freedom to think and believe as one chooses; freedom of conscience. Without that, there is no genuine democracy. But, more to our point, without that, there is no genuine religion. The only possible guarantor of such freedom, as the Founders understood, is a magistrate who acts with absolute religious neutrality. Religious people, that is, need the separation of church and state as much as atheists do. That separation, in fact, is why religion thrives in America.

It's a paragraph from an article called "Secular Rule Benefits the Faithful, Too" by James Carroll.