I haven't outlined all the points elaborated in the article leading to that either/or conclusion; however, I harbor a skepticism towards all binary options. If it isn't possible to make moral judgments without reference to absolutes and those absolutes are most often found within religious systems, it would seem to follow that engaging in rational discourse regarding what is considered right or wrong, good or bad, would be fruitless; the ultimate reference point would be an article of faith. If we were discussing the morality of abortion, after one person arrived at his belief in the sanctity of human life from conception and the other arrived at a person's right to choose, we would be at an impasse. The person basing his position on the right to choose may assert that such a right is inalienable and-God given, which simply confronts us with conflicting absolutes. On the other hand, he might ague that the right to choose is based on the sort of society in which he prefers to live: a relativistic, factual statement which some would claim to be irrelevant from a moral perspective.
I would suggest that there is another option that historically preceded the theory that moral judgments have some distinct sort of linguistic or epistemological quality, distinguishing them from statements of fact. Aristotle's ethics provide an example; one that I believe has much to be said for it. As I would paraphrase that approach, it is based on the assumption that were we to adequately understand what it is to be a human being, as a specific species, we could draw some conclusions as to what conditions and behaviors are needed for that species to flourish. If we regard such a condition of flourishing, what Aristotle refers to as happiness or living-well, as our goal in life, whatever promotes that goal is good and whatever negates it is bad.
Within that classical perception, what is regarded as good and bad, right and wrong, are derivative from some final end. If we know the function or distinguishing activity of the sort of thing we are considering, we can derive what characteristics are needed to be a good thing of that type. For example, amongst a selection of knives in our kitchen, we choose with knife is good for a particular purpose. Aristotle claimed that the characteristic, distinctive activity of humans is the capacity to make reasoned choices; hence, what enhances that capacity is good, what negates it is bad. One could argue, for example, that starvation is bad, since it negates our capacity to make reasoned decisions, while to be adequately nourished enhances that capacity and is good.
The Aristotelian concept of morality is one of the foundations of what came to be regarded as natural law; later corrupted by religious philosophers through its subordination to what was taken to be divine law. Whatever one thinks of the content of various understandings of natural law, the logical form of its argumentation seems to me to be sound. Its ultimate foundation, what is considered to be a human, is taken to be a fact; not an absolute of a religious or totalitarian world view, but something to be determined through observation and reasoning. The field of evolutionary ethics is a contemporary manifestation of such an approach.
If we understand nihilism in its usual sense, the belief that nothing, ultimately, matters, one is free to take the position that the flourishing of the human species is a matter of indifference; a logically possible position that is likely to be held by a very small minority. In my opinion, it is more a pose than a perspective that can be seriously maintained. Like Diogenes, you can be a cynic and live in a box in the public square, but even to the original cynic, it mattered that he be in the sun. Similarly, if you were a believer of a certain sort, you might be indifferent to the well-being of humans, since that is insignificant in comparison to the glory of God. Again, it is to be hoped that such a belief would be appealing to a very small number of people.
Unfortunately, there is never likely to be enough of a consensus related to what it is to be a human being or what would constitute the flourishing of the species to result in a concrete code of morality; whatever consensus could be reached would likely be of a very general variety. Nevertheless, it might be helpful to work toward whatever consensus could be reached. Agreement might be possible around general principles, such as the distribution of the world's resources, combatting disease and pollution and not inflicting harm on the innocent. The devil would be, as usual, found in the details.
In order to arrive at a more detailed ethics I would supplement Aristotle's approach with a utilitarian dimension; postulating that good and bad, right and wrong, are derivative from our preferences in relation to what it would be for humans to flourish or to live well; implying a form of social organization in which we would want to live. For example, I, personally, would want to live in a society in which no one suffered from a lack of the basic necessities of life; in which there was truly an equality of opportunity; in which individual differences were valued; in which the common good of the community trumped individual accumulation; in short, what is called a social democracy. What promotes such a society I would regard as good and what negates it I would regard as bad. There is no reference to any absolute; only to what I regard as a desirable society in which human beings could flourish. There is no slippery slope towards nihilism, as I am committed to the importance of moving toward such a society; just as I imagine those who hold a different ideal are committed to their vision.
In regard to differences as to what is desirable, it can be hoped that a reasoned discussion can take place in which we try to convince each other and others to move closer to our preferences. Hopefully, we could agree that all points of view have a right to be expressed and that the majority preference should prevail. Those who find themselves in the minority can either stay and argue or leave to live in a society more to their liking. Social democrats and capitalist libertarians, for example, can discuss forms of society which they think will best promote human well-being with no reference to a moral absolute; a form of discourse with which we are quite familiar; though it seems to be increasingly corrupted through appeals to religious beliefs.
When those whose morality is grounded in some sort of divine inspiration are in the minority, it is sometimes possible to reason with them; support for freedom of speech, conscience and basic civil rights is something they might embrace when it suits there own interests. However, characteristically, once in the majority, they want to impose their own moral codes on everyone. Once they have the power, their beliefs prevail over all other values; for example, abortion, based on their understanding of the sacredness of human life, automatically trumps a belief in an individual's right to choose. In the face of moral beliefs based on absolutes there can often be no discussion; for someone such as myself who has no desire to live in a society where such values prevail, the only recourse is to do what is in our power and consistent with our own morality to prevent their having control. Such resistance is grounded, not in some competing absolute, but in the fact that neither I, nor, it is hoped, the majority of my fellow citizens, want to live in a society controlled by the beliefs of a particular religion. When a society elects, democratically, to live within the moral code of a particular religion, the most that one can hope is that they allow those in the minority to leave in peace.