Here the deontologist is arguing for the principe 'killing is wrong regardless of the consequences' (deontic) but uses a poor justification for which consequentialism is a more reasonable conclusion. So the 'deontologist' is wrong even though his principle cannot be externally verified. I was just (unclearly I see) using this strawman to illustrate how theories could be better and worse at explaining what they attempt to explain without being the sorts of things which can be proven. I will attempt to be clearer in future.