I preface this by saying that I recently converted to veganism, so it pains me that I'm lumped in with these idiots. I did not stop eating animal products for the benefit of any animal except myself. I believe that the natural order of the animal kingdom involves death and suffering, and animals will eat animals. I don't think that means that I need to eat animals, but that's neither here nor there.
These idiots are trapped by their own inconsistent ideology because they have members who want to help animals and therefore want the shelters to run, and then they have other members who think even owning a pet is cruel to animals (so why have them around to adopt?), and I think that the presence of the shelters, but the almost blase way in which they kill animals reflects that split in their member base. There's no way to reconcile it, so they do both badly to keep both sides equally unhappy.
The real losers here are the animals that could go to good homes.