Perhaps I'm a bit cynical, but I don't believe slavery or states rights was really the underlying cause of the Civil War. I believe the Civil War was a power struggle between two radically different elites: the rich Northern Industrialists versus the rich Southern Plantation Owners. Up until the time of the election of Lincoln, the balance in both Congress and the Supreme Court had favored the power of the Southern Plantation owners (as evidenced by the Dred Scott Decision). By the time of Lincoln's election, the Northern Industrialists were gaining control over the Federal Government. These elites sold such concepts as the North impinging on the rights of Southerners (when the only right really being threatened was the right to own slaves, a right exercised only by the top 5% of Southerners economically) and the abolition of slavery (when Lincoln himself had stated that if to preserve the Union he had to free none of the slaves he would have) to the other 95% of society, and had them die in the millions over the power struggle.
As far as Shiloh's point about States Rights versus the control of the Central Government, I'm sorry to say that the framers of the Cosntitution completely disagree with you. Before the Constitutional Convention, the U.S. existed pursuant to the Articles of Confederation, perhaps the document tp which Shiloh refers. However, the loose confederation without a centralized government did not work, so the Constitution was drafted. The principal aggitators for the drafting of the Constitution were Hamilton, Madison and Jay, the authors of the Federalist Papers. A reading of these papers demonstrates that the framers saw the need for a strong central government to ensure the survival of the States as against both internal and external threats. The dominance of the central Federal Government over the States was again clearly demonstrated by the Dred Scott Decision, where the Missouri Compromise, along with an individual free state's right to ban slavery within its own borders was overrun by the Supreme Court.
Shiloh is correct that under a fair and rational reading of the Consitution, the Federal Income Tax is unconstitutional. The Constitution requires that any Federal Tax be levied equally among the several states. Pursuant to this article of the constitution, several attempts to levy an income tax (which by definition cannot be levied equally amongst the States) were struck down by the Supreme Court. Then, the Court, packed by political appointies, reinterpreted the plain language of the constitution to permit for an income tax. That is another unintended side effect of the Constitution. The Supreme Court was never expressly intended to have the power to determine constitutionality (a power the Courts in England, upon which our legal system is based, do not possess). The First Justice Marshall's opinion in the famous (perhaps infamous) Marbury v. Madison decision claimed this right for the U.S. Supreme Court, thereby empowering 5 of 9 old men (and later women as well) to undo the will of the people and change the meaning of the words of the constitution, adding to and subtracting from it as they choose.
When you think about this, as well as all the undemocratic institutions built into our system, including the Senate (where the 10 people in Montana have the same power as the 10,000,000 people in New York) and the electoral college (where not only does a majority of the popular vote not guaranty a victory, but where the electors are not even legally obligated to vote the way their state voted!), its quite frightening.