Wizard, I think the point Arthur was trying to make is this:
The assumption made is that there is a fixed pool of funds. Either you need to tax the rich in order to fund the tax cut in the middle-class, or you need to tax the middle-class to allow the rich to get tax breaks.
What Arthur was trying to get you to do, is to ask why both "classes" can't get tax breaks. Leaving the money in the hands of the people, leaving them to choose where to the money goes. Why must government have the money, why must the state be the one to choose where to spend it, why is the state more "knowledgable" than individuals bearing in mind the fact that individuals value different things in different degrees.
Let's have some common sense here, the state will spend it in a manner that makes them look good, I.E. it allows them to get more votes. Since there is no profit on the construction of roads, infrastructure etc.(As the state is not a business) you cannot measure if any of those projects are increasing overall wealth or not but the state gets to show some "statistics" about how many jobs they created, completely ignoring the fact that leaving the money in the hands of people means that it would have either been spent (Increasing demand for present goods, thus potentially securing current jobs and creating more) or been saved and invested which makes capital available for companies to potentially build more factories (More jobs) buy better machines (More jobs for manufactures - assuming it is made in US).
Even if the various state projects create more jobs, you cannot measure the potential "loss" of jobs that would've been made in the private sector, so you cannot know if the project was overall a success in creating jobs (If thats the criteria you are using to measure success).
Arthur basically wants you to dig deeper and ask more questions.