The heart of this article is this:
"So I merely want to pose a question: If the atheists are right, what would be the effect on human morality?"
Later it is re-expressed in this way:
"So the dilemma is this: How do we choose between good and bad instincts? Theism, for several millennial, has given one answer: We should cultivate the better angels of our nature because the God we love and respect requires it. While many of us fall tragically short, the ideal remains."
As people know who watch or listen to our shows, we've grappled with those questions frequently in recent years. The problem with the question "How do we choose between good and bad instincts?" is that it's a non-trivial philosophical issue, about which tremendous volumes have been written by philosophers for many centuries. Folks like Michael Gerson believe that they have scored a good point when they essentially ask us to give them an simple answer in a thirty second sound-bite or even an 800 word column. Then they falsely assert that religion provides that easy answer.
You want a sound bite? As always, take a cue from the Euthyphro Dilemma. You don't need to play the game of trying to appear to have all the answers; it is sufficient in this case to point out that theists do not have any answers either. The counter-question is "How does inventing a god help us to choose between good and bad instincts?" Then you can follow up immediately by pointing out awful things that God can and does ask people to do in the Bible. You can take your pick from slaughtering entire cities and taking the virgin girls to be unwilling brides; being prepared to stab your first born son to death as a test of loyalty; millenia of unabashed support for slavery; etc. Not to mention modern applications of religion, such as flying planes into buildings.
In this case, pleading "That's the old testament" or "Only Muslims fly planes into buildings" is completely irrelevant. Michael Gerson didn't make an argument for modern liberal Christianity; he made the more general claim that believing in a higher power solves the problem of morality. Of course it doesn't. Belief in a higher power simply adds a level of arbitrary abstraction to your moral decisions. You are no less likely to commit acts of atrocity, only now you are free to attribute these actions to the deity of your choice. Instead of picking your morals, you are picking your god, as well as your interpretation of what the god wants.
Here in the west, only a few extremists are willing to take Biblical morality at face value, including (for example) stoning unruly children to death, but these are not the sorts of people you want to spend much time talking to. Most people are ready to argue that they shouldn't be expected to accept some of these edicts that were supposedly directed by God. At that point, the question of "Where do you atheists get their morality?" is easily answered: "It's probably about the same place YOU get your morality, since it clearly isn't from God."
That's most of what the article is about, although there are a couple of other assertions that are worth commenting on. The first paragraph of the article says:
"British author G.K. Chesterton argued that every act of blasphemy is a kind of tribute to God, because it is based on belief. 'If anyone doubts this,' he wrote, 'let him sit down seriously and try to think blasphemous thoughts about Thor.'"
Right. That totally makes sense. Because every time you criticize something, you are secretly supporting it. Doesn't matter what it is. If you stop and think "Hey, I saw my mom sneaking around my bedroom, I wonder if she left that money under my pillow?" you are paying tribute to the tooth fairy. If you say "Suicide jihadists are idiots to believe that they will get 72 virgins in the afterlife" you are paying tribute to their notion of an afterlife.
I wonder if anyone will ever catch on that this argument boils down to nothing more than "I know you are, but what am I?"
Gerson also states:
"And I suspect that a certain kind of skeptic would remain skeptical even after a squadron of angels landed on his front lawn."
This, too, is a fairly common desperate move to use against atheists. Theists realize that the actual evidence that is available to prove the existence of God is piss-poor, so in frustration they make up hypothetical rock solid evidence, which does not really exist. By making the unsupported claim that atheists wouldn't even believe THAT, they manage to shift the discussion away from the poorness of the actual evidence, and turn it into an unwarranted assumption about how unreasonable atheists are in their imaginary alternative universe.
Still, just so we are clear, let me state this for the record. If a squadron of angels landed on my front lawn and started chatting me up about God, I'd be pretty easy to convince at that point.
There. Now God knows exactly what he can do to make me renounce atheism. Where's my squadron of angels?