All "pork barrel" together is relatively small peanuts compared to the budget as a whole. It's there, but you won't be able to cut taxes much by eliminating the obvious pork barrel excesses (and even that would be tough politically).
Of course it would be difficult to eliminate. However, I include not only the pet projects of several members of Congress, but also other narrow and locally tailored spending, including several appropriations relating to defense (remember the big fuss about BRAC?), transportation, agriculture, the interior, energy, and education.
To a degree you are correct, but we can still consider the theoretical virtues of a hypothetical tax plan, regardless than a the probability of it being implemented in the first place.
Of course, I don't think that we are necessarily advocating such flat rates, which would for the highest earners be pretty much the same as the current effective rate anyway.
Naturally, it's non-discretionary spending that should be cut. I believe that it occupies about 2/3 of the federal budget. For example, assuming that we are considering politically realistic options, Medicaid spending could be cut by fixing the federal contribution at 50% of the total cost. Currently, the federal government on average funds approximately 60% of Medicaid. States, thus, are less likely to be fiscally responsible, when they know that the bulk of the tab is being picked up by the federal government. Reducing the federal contribution would encourage states to be more careful in Medicaid spending, and would probably save about $50 billion, if not more.
Similarly, the Prescription Drug Benefit should never have been approved. It's a highly irresponsible measure that will eventually cost the government billions.
Such measures, with respect to non-discretionary spending, would eventually add up sufficiently to ensure that the budget can be balanced.
That assumes that lower tax rates would necessarily yield less revenue, which is at the very least a debatable premise. Lower taxes (especially lower corporate taxes and capital gains taxes, and an elimination of the AMT) would probably encourage more economic growth, and thereby increase overall tax revenue. It would depend, however, on one's perception of the Laffer curve.
Here I would agree. The long-term effects of appropriate reform would undoubtedly be highly beneficial, though in the short term it would be politically suicidal. I feel that Lyndon Johnson's "War on Poverty" is particularly responsible for this mentality.
It is curious that the current state of affairs was brought about precisely by such a crisis.