One of the major alleged positive points put forward by secularists for a secular civil society is that secularism is religiously neutral. Once that's established, they usually go on to tell you why you're wrong and they're right about how civil government should be done.
I hope you caught the irony in that. The fact is that religious- or worldview-neutrality is impossible, because any system of laws and public policies will inevitably reflect some people's worldview assumptions over those of others. Ethics is nothing other than applied worldviews, and civil law is nothing other than publicly applied social ethics. So long as there are multiple worldviews represented by those who live in the society (which will be the case in any society that contains more than a handful of people), the law will reflect some views and reject others. Secularism is nothing other than the establishment of Agnosticism/Atheism as the official religion of the society, to the exclusion of other worldviews (other worldviews may be tolerated to some extent, but only at the sufferance of the values of the established worldview).
This basic argument for the impossibility of religious neutrality in civil law has been made lots of times and by many different kinds of people, though it has failed to gain a strong foothold in the general American psyche at least partly because the entire American project of "religious equality" is rooted in the idea of religious neutrality. To admit that the latter is impossible is to give up on the mainstream idea of the former and thus to give up on something that is seen to be a part of America's core, unique identity.
Below I have provided links to an array of articles making the argument against the possibility of neutrality. The articles represent the thinking of very different people with very different worldviews but who are united in having come to admit that neutrality is impossible and in their choice to speak out about that fact. These articles can provide a place to dive in for those who wish to think about this issue with greater depth.
First of all, one the best mainstream academic authors I have come across in the modern day who points out the impossibility of neutrality is Steven D. Smith. Smith is a University of San Diego law professor.
Here is a list of his books on amazon.com. They are all excellent.
Here is an excellent article he has written entitled "The Paralyzing Paradox of Religious Neutrality."
Here are some more great articles on this subject:
Is Secularism Unprincipled? - by Ian Polluck. Polluck is an Atheist, but one who recognizes the inherent hypocrisy of the secular project so often favored by modern American Atheists (though he advocates for it anyway even while recognizing its hypocrisy).
Down with Secularism! - by Richard Smyth, another Atheist who recognizes the non-neutrality of secularism.
Is God Unconstitutional? - by Phillip E. Johnson of Intelligent Design fame. Johnson provides a very perceptive analysis of modern popular, legal, and academic cultures and how they are influenced by Naturalism (Agnosticism/Atheism) despite their claims to be worldview-neutral. His book Reason in the Balance is a fantastic work along these lines as well.
I'll also add a couple of articles I have written on the subject on my blog:
The Impossibility of Neutrality
The Impossibility of Governmental Neutrality in Religious Matters
As I continue to think of more articles and books on this subject, I'll add them periodically to this list as updates.