Even in slaughtering cattle there are specific laws on how it must be done to make it more humane. One cannot, for instance, slam the cow/bull into the ground until it is dead, or hang it, or electrocute it. Of course, a rancher knows that adreneline makes meat taste differently and would avoid all of these things as well or he would likely end up selling less of his stock in the end.
Animate property are different than, say, a fence post.
Well, that only addresses how you slaughter the dogs.
I agree, as I mentioned in my best argument for illegalization, it's not a fence post.
Still, there is no clear distinction on what is cruel. That is why I suggest a supermajority, which I'd guess would be easy to achieve in this case.