His musing defies belief (which I guess means that I have no "faith" that Velleman was serious when he wrote it). In English (especially American English), "usage is king" (as my sister, the linguist, is very fond of saying), and it simply cannot have escaped David Velleman's perceptual abilities and great intellectual capacity to notice that a substantial majority of Americans use the phrase 'people of faith' to mean those with faith in monotheism in the Judeo-Christian tradition.
So I assume that what Velleman really means (though it's hard with philosophers to know what the meaning of "meaning" is), that he wonders why, given that everybody has faith in something (and that something can, in his opinion, lead to a moral existence), people should care whether or not that the faith is a Judeo-Christian faith.
Why indeed? Well, perhaps that's because when people have veered away from Judeo-Christian beliefs in the past, really terrible things have happened: facism and communism to name a couple, each of which contributed to the wars and geno/politicides than killed many tens of millions of people. Indeed, an anthropologist once told me that the wars and geno/politicides of last century killed more people than had been previously killed by such conflicts since the beginning of time.
Further, I hypothesize that if the United States had not had strong Judeo-Christian beliefs in the early part of the last century, we would have ultimately embraced communism (it was, after all, a very powerful and compelling idea), and without the United States and other countries that stayed the course with us producing new technologies that the whole world, including the communist block, benefitted from (and survived because of them), the world would have been plunged into a new Dark Age, from which, judging by the economic and ecological disasters in the communist block such as Chernobyl, might have, by now, led to the extinction of homo sapiens (but don't worry, cockroaches would've survived, so life would've continued on).
I'm sure J. David Velleman is a profoundly moral person with the best intentions. But, it seems to me he is incorrectly projecting his own six sigma capabilities in the area of reasoning, intuition, belief, etc. onto a species (that'd be us homo sapiens) where such capabilities are extremely rare. In other words, if we all had his capabilities and hung around and studied philosophy all day, the world would be a better place.
But we don't.