[Your preferred theory of ethics] is tenable when examined closely

I would like to begin by saying that I agree with your definition of 'tenable'. Having established this, I would like to point out that while Pro's points are undoubtedly a clever circumvention of the arguments I've presented here, they fail to address the core issues I have established. I will demonstrate how by discussing each of the sub-cases presented above by Pro. Sub-Case 1: The Impossibility of Calling a Method of Moral Decision Making Wrong This is a good argument to establish why I could not claim that the conclusions drawn from an ethical theory are 'wrong', unless I could prove that another system of thinking was objectively more "right", except... That is not what I am claiming here at all. I have not been claiming that the conclusions drawn from utilitarianism are wrong, but rather that no conclusion at all can be drawn from an exclusive interpretation of utilitarianism. A defensible theory must have predictive power. In other words, if we know what the genuinely true answer to a problem is, and we apply a working theory to this problem, the output of the theory needs to agree with the true answer in order for us to say that the theory is working and defensible. It does not matter, in this case, that I do not know what the true answer is, if the theory does not predict any solution to the exclusion of all others. Pro's statement that "The only way to prove the being inconclusive is evidence of Utilitarianism being flawed would be to produce a different result with a non-flawed moral system and compare the two" is incorrect. All I have to do is demonstrate that utilitarianism does not discriminately choose any solution, which I have done, and which Pro has already agreed with, in my last argument. Sub-Case 2: The Moral Method and The One Applying It are Separate Entities You may have noticed, while reading through Pro's argument, that there was something distinctly fishy about the logic being employed here, and you would not be wrong. Before I address why it is wrong, I would like to propose a new theory of ethics here to consider. When faced with a moral dilemma, you should make your decision based on how many people in the room are wearing blue hats. How, you might ask, are we to interpret that in a way that gives us any kind of solution to the ethical dilemma? Well, fear not. According to Pro's argument here, it doesn't matter how absurd the theory of ethics we propose is, if anyone has an issue with that theory, it is apparently the fault of the interpreter, and not that of an incomprehensible, inapplicable theory. We can not establish that a theory is incomprehensible unless we know the true answer that it ought to be able to predict, and yet arguing that it predicts no single solution is somehow not adequate to dispel this blaming of the interpreter. Sub-Case 3: Most People Will Conclude the Same Result Using Any Method This whole argument is diverting the issue. We are not asking how well people practice the ethical standards they claim to follow, the question is whether those ethical standards hold up to examination. Very few people actually understand or practice particle physics, but that does not mean that the field itself can't be tested and scrutinized. Sub-Case 4: The "We Can't Know The Consequences" Point Is Irrelevant I will actually grant Pro this point. I think his/her argument is valid here. Sub-Case 5: Laws and Utilitarianism In contrast to his/her last argument, this one makes very little sense. I could see it very easily being argued that the uproar to give women the right to vote, or to legalize gay marriage, or to give slaves their freedom were all instances where the benefit to the many outweighed the inconvenience of the few. Not only does the argument not really work, but I fail to see it's relevance, so I will not be discussing it here further. To summarize; clearly defined words and definitions and phrasing are all important in the codification of any sort of ethical system. We do not have an overview with utilitarianism that adequately and prejudicially allows itself to be applied in the selection of any specific or general most ethical option in a scenario, and it is therefore indefensible as a moral position. Where we are asked to select options for 'the greater good', we have no idea whether this would apply to butchering an innocent person to salvage their organs, or to release all serial killers from prison in the interest of reducing the taxes put towards incarceration costs. It does not matter whether or not we can say the solutions utilitarianism gives are incorrect, when it is plain to see that utilitarianism gives it's interpreter any solution they wish to find. Thank you for the debate.