A reposting of Bruce Thornton's 2004 essay of the above title. A quote:
If Judeo-Christian belief is so central to the ideals that created our government in the first place—if, as de Tocqueville wrote, "Freedom sees religion as the companion of its struggles and triumphs, the cradle of its infancy, and the divine source of its rights"—then the current anti-Christian fundamentalism strikes at the root of our political order. For if we are, as the secularists tell us, mere material creatures bound to one another only by contractual relations to be dissolved or altered at will, then what will provide the basis for all those selfless actions and emotions that any community depends on for its cohesion, and that keep freedom from degenerating into mere license, the power to do and consume whatever gratifies our selfish will and appetites? Where will fundamental values come from, all those beliefs that bind us into a community, and that we are willing to die and kill for, not because they have been scientifically proven but because we believe passionately that they are right and true and will benefit the greatest number of people?
The secularists have failed to provide an alternative for the religion that they have discarded. Into this vacuum has rushed any number of pseudo-religions, from Marxism to scientism to environmentalism, that are infinitely more irrational and mischievous than traditional Christianity. Yet this secularism is the creed dominating the schools, one more dogmatic, more intolerant of dissent, and more prone to self-righteous hypocrisy—in short, more fundamentalist than the beliefs of most Christians. For those concerned about the dangers of religion to our political life, then, look to these creeds, which are passed off as the fruits of science and reason, rather than to a Christianity that has been banished from the political culture it helped to create.
The whole essay here.