After some reflection, John Culhane mostly takes my point:
One immediate result [of the discussion] was a conversation with my spouse, David, who is the one in the family with true empathy. He was astonished that I’d even raised the question of the humanity of anencephalics, uninterested in the logical case I was able to build for that possible conclusion. Eschewing metaphysical terms like “soul,” he simply stated that these babies were entitled to respect. It’s really impossible for me to argue with that. I realized that part of the problem is that we generally afford so little respect to other species that when babies without cognitive capacities appear, thinking of them as similar to other animals with lower cognition can lead to a cold place. For me, then, this conversation is a reminder that humans are part of a larger, teeming universe, and that we mostly do a terrible job of remembering and respecting that.