Then I got to codgitating.
It is increasingly common nowadays to deride any suggestion of human specialness or uniqueness as "speciesist" snobbery. We are all animals, and human morality is based on minimizing undue suffering, the argument runs, so we are morally obliged to minimize the undue suffering of our fellow animals, even if they are not "human" like us.
Here was my worry, however: If granting moral immunity to non-human animals is a moral imperative, why don't non-human animals themselves grant such moral immunity to each other? More to the point, if non-human animals are "effectively" like us (which is just the way moderns say "essentially" the same, without having to say dirty words), why don't they assert their moral demands for themselves?
If non-humans need us to prop up their equally intrinsic moral worth, then we are different from non-human animals in a crucial way, namely, in that we can recognize and institute moral worth. Precisely by arguing that we must protect animals' moral dignity, anti-speciesists undermine their own core thesis, since the intrinsic moral duty of protecting non-human dignity is a special prerogative of humans.
Further reflection leads me to see that not even humans can "give themselves" intrinsic moral worth, since giving implies taking, and nothing intrinsic can be given or taken at will. Therefore, the intrinsic moral dimension in being-a-human cannot be something humans make for themselves, and therefore must come from another source. Plainly, it does not come from non-human animals, since they are precisely the creatures whose need of moral amnesty started this whole codgitation. Will a naturalist say that Nature bestows "intrinsic moral dignity" on humans? I doubt it. For according to Naturalism, humanness is no more intrinsic to the natural order than barnacleness, and so the only intrinsic traits natural entities may have are those which are common to Nature as a whole (i.e. mass, size, charge, etc.).
So it seems arguments against speciesism are arguments for a kind of theism, but theism inevitably implies a special status for humans as those in contact with God.