I think that most people today believe that a non-religious approach to an issue is the only fair way to discuss it. For example, when the question of same-sex marriage is discussed, any argument that comes from any kind of religious source is not allowed in most discussions and debates. The fact is, however, that we all approach these kinds of questions from a particular religious point of view.
Religions make statements about the ultimate reality that undergirds the physical world in which we live. From this ultimate reality come ideas of good and evil which affect the decisions we make. It is impossible to make a meaningful decision without any idea of good and evil. I chose to eat Cheerios for breakfast this morning because oats are supposed to improve the health of my heart, and I think good health is a good thing.
Here is what I observe are the morals of many who approach issues from a non-religious point of view, which I will call secularism. Happiness and self-fulfillment is good, but suffering is evil. Equality is good, but anything that treats any class of people differently is evil. Love is good, but anything that interferes with the expression of love is evil. The only difference between secularism and any religion is that there is no supernatural basis for its beliefs. The only basis I've seen is that this is what a particular group of people agree is right. If you think a particular thing is good, and there are enough people who agree with you, then that's your basis.
Some say that they have a morality based on science, but science is incapable of making moral values. Science can tell us why we feel pain, but it can't tell us that pain is bad. Indeed, science tells us that pain is a survival mechanism. Science cannot even tell us that it is better to be alive than to be dead. Science can try to predict climate change, but it cannot tell us if it is good or bad. Costal cities might be flooded by rising sea levels, but is that bad from a scientific point of view? Does the universe care about New Orleans?
Others say that they use Philosophy as a source of moral values. This is better than Science because at least morality and ultimate reality are in the purview of Philosophy. However, Philosophy must address the claims of religion if it is to claim an answer for ultimate reality, and there is no philosophical consensus that has been able rule out religion and establish a secular moral framework with which we can all agree.
There were two important atheistic philosophies that inspired significant social movements. The first is the materialistic philosophy of Karl Marx, which was behind the totalitarian Communist regimes that arose in the twentieth century. The second was Friedrich Nietzsche's atheistic philosophy of power, which inspired Adolph Hitler's idea of an Aryan master race that was destined to rule the world.*
Today's secularist cannot point to a philosophical genius such as Marx or Nietzsche as a foundation for his views, but like both of them, he has chosen to reject a religious basis. In doing so, he has made a religious choice. There is nothing conclusive to demonstrate that his secularism is superior to any supernatural religion. Indeed, the novelty of today's secularism means that it is untested regarding long-term results. So, for example, since there is no history of any significant practice of same-sex marriage, we don't know what will result from it. I am not claiming that this is a conclusive argument against same-sex marriage, but I am claiming that there is no reason to automatically prefer the secular point of view.
We live in a culture with many different religious views; how do we decided which one to follow? Ultimately, we have to work something out that we can all live with if we want to maintain a free society. We have to have a conversation where all can participate. We cannot silence a voice because it is religious.
*See Eric Mataxes, Bonhoeffer - Pastor, Martyr, Prophet, Spy, pp 168-169.