Ross Douthat writes

. . . much of today’s liberalism expects me to respect its moral fervor even as it denies the revelation that once justified that fervor in the first place. It insists that it is a purely secular and scientific enterprise even as it grounds its politics in metaphysical claims. (You will not find the principle of absolute human equality in evolutionary theory, or universal human rights anywhere in physics.) It complains that Christian teachings on homosexuality do violence to gay people’s equal dignity—but if the world is just matter in motion, whence comes this dignity? What justifies and sustains it? Why should I grant it such intense, almost supernatural respect?

This seems largely correct to me. A coherent secular morality is a tricky problem in and of itself. One that makes absolute claims even more so, and one that makes absolute claims absolutely seems well beyond our grasp. And, I say this as a secularist who is very much concerned with ethics or what, to make the point, I have often been forced to call the-ethics-game.

For example, the claim that slavery is fundamentally wrong in all cases is not controversial among secularists but it is far from clear how one justifies this except by asserting it. And, then of course what is one to say to people who deny it?

Intending no disrespect to the underlying issue, the argument seems to devolve into “na-na na-na boo-boo.” Which is to say, simply refusing to accept the denial as valid.

There are various claims which amount to saying the human faculty of reason endows us with certain inalienables. Not only does this strike me as blatant post hoc speciesism, but it seems to suggest that there is some mental threshold below which a person could fall in which not only enslaving them would be fine but also violating any of the other rights which are asserted to stem from self-ownership. In short treating the person as an animal.

Attempts to reconcile this problem back people into corners such as asserting that the well-being of an adult pig is as important as the well-being of a newborn baby.

At least some of the confusion over this comes from the assumption that lacking the same ethical grounding as Christians, secularists either will not behave morally or cannot make moral demands.

The first I think just misunderstands how people behave and gives too much credit to critical reasoning and justification. For the most part secularists behave morally for the same reason just about everyone else does, because they would feel bad if they did not.

The second I am increasingly tempted to say conflates cultural politics with the ethics-game. If you ask on what grounds do I accuse rapists of having done wrong, then the authentic answer is that a world with rape displeases me and this is a tool I can use to get society to impose sanctions against it.

That in my mind is quite different than the ethics-game. The ethics-game is an attempt to answer the question, what moral stance “should” I adopt. It is in the ethics-game that we pay careful attention to metaphysical coherence, consistency and an attempt to tease out what we really believe.

What Douthat appears to be saying is that the ethics-game is hard for secularists, and that is correct.