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

Stating that I have the burden of proof is a good tactic, but I don't think I'll have too much trouble here. To begin with, any choice that we can make as a society must be accepted to have both positive and negative consequences, and most particularly those that require the application of a code of ethics like utilitarianism. Even if we were to use a utilitarian argument to say something to the effect of 'people who are apparently dying when they come into the emergency room should be treated before their possession of insurance is known, if they are not conscious when brought in". Most people would agree with this, yet there will certainly be an increase in taxes or insurance rates as a direct result of this decision. Knowing then that all of these decisions have negative, as well as positive, outcomes for different groups within a society, the application of utilitarianism must then be applied arbitrarily to any side of an ethical issue. In the above example, you could argue for the treatment of an unconscious man with a bullet wound, because the severity of his individual suffering outweighs the minor inconvenience of the population at large for their slightly increased taxes. You could, however, just as compellingly argue that if we can establish any comparative scale for economic burden vs. physical suffering (which we can't, because utilitarianism does not provide us with these basic conversion tools which form the basis of the issue it is trying to address), we would find that any reasonable amount of value placed on economic burden is going to win the argument when that burden is multiplied by the number of tax payers. This argument may seem harsh, and you could, if you liked, apply the utilitarian argument to libertarianism and try to weigh freedom against suffering, but our results would remain the same; inconclusive. The only reason we believe that utilitarianism might apply in the above instance to helping the single dying man is because the ethics we have instinctively adopted as social creatures in our particular culture is more likely to dictate an empathetic response, and so we will see how we can shape utilitarianism to fit the ethical answer we already believe to be true. To be clear though, utilitarianism has not aided in any way in that decision, regardless of the side you fall on, because the "amount of good things" could be interpreted as any intensity of gain for the most number of people, or favour high intensity of goodness for a smaller group. We do not know which, because utilitarianism offers us no tools for making relative comparisons; all it provides is argumentative support for pre-existing ethical prejudices. As if utilitarianism's inability to truly relate virtually any two sides of an ethical issue to any kind of relative value, which is basically the only thing it sets out to do, wasn't bad enough, it is not even reasonably applicable when you know which ethical consequence is more desirable. Utilitarianism fails at such a fundamental level because it claims that we should base our decisions on consequences when we obviously have no ability to know, with any degree of certainty, the consequences of our actions. In the example used here, admitting the man to the hospital may save his life, but it may not, it may increase insurance rates and taxes, but that's uncertain too. Not only are we left wildly speculating as to which consequence utilitarianism supports, but also as to whether or not a certain action will even yield an expected consequence. In short, utilitarianism's "increasing the amount of 'good things' in the world" is the equivalent of the "do the right thing" statement; it sounds pretty, but no one knows how to apply it. All of this, and we haven't even touched on the fundamental hedonistic assumption of utilitarianism; that happiness is the highest ethical goal, which is obviously unsubstantiated by anything except personal feelings.