Part of the problem I'm having is that humanity is the reason dogs aren't wolves roaming the wilds seeking prey on their own (that's probably a net benefit for dogs since, despite no documented cases of a wolf attacking a human, we hunted that species to near the brink of extinction). Playing Malthusian games with the ratio of dog food/shelter to the total dog population is a bit disingenuous since the very existence of dogs means we're no longer dealing with a purely natural system, but one artificially influenced by man. More human intervention is probably the responsible thing to do, but intervention in the form of mass killing for the sake of convenience while calling it "humane" seems disingenuous and slightly immoral.