Alistair Campbell once famously said, when Tony Blair was asked a religious question, "We don't do God."
Although both Tony Blair and George W Bush were both clearly sorts of Christians, what Campbell meant was that religion should be kept as a private matter and not be allowed to enter the public discourse. This view has been endorsed by well-known secularists like Peter Singer, EO Wilson and Daniel Dennett.
But what is religion? Some say it is a form of belief in God, but that would exclude Buddhism which does believe in God at all. Some would say it is a belief in the supernatural, but that would exclude Hinduism which admits to no supernatural beyond the natural world. A better definition is 'a set of beliefs which explain what life is all about'. Perhaps the most popular set of beliefs in Western Europe today is that the material world is all there is; that we are here by accident and that when we die we rot. Therefore the most important thing is to choose to do what makes you happy and not let others impose their beliefs on you. The point is that even secular pragmatists come to the table with deep commitments and narrative accounts of what it means to be human.
We all live according to a fundamental set of beliefs about what our existence means and we act according to those beliefs. To exclude 'religious' principles from public debate is to favor the secular point of view in a biased way, just as much as Islamic countries favor a view that Mohammed's name must not be sullied.
In fact secular grounds for moral positions are no less controversial than religious ones; all moral positions are at least implicitly religious and rely on 'givens' that are neither self-evident not logically provable.
Although many continue to insist on the exclusion of religious opinions from public debate, many thinkers, both religious and secular have come to recognize that such a call is itself religious.