Do not fucking condescend to me on American history. Your historical and political knowledge is sorely lacking and tainted with Southern bias. Firstly, A state exist to serve and protect it's citizens. Cannot do this if the borders of the state are constantly uncertain, and the constituent parts of the state are constantly fighting with each other. If the states that currently send more money to the federal government then they receive decided to secede tomorrow, leaving the other states behind, it would cause chaos. The ideas of the Articles of Confederation were still extant at the time of the Constitution's creation. However, the federal government needed more power in order to keep the union from dissolving. The Constitution was created in order to keep the country together; allowing states to secede at will if they didn't like the policies of the government would be disastrous and and antithecal to the reason for the constitution in the first place. Besides, the constitution says,

We the People of the United States, in Order to form a more perfect Union…,

Not,

We the People of the United States, in Order to form a more perfect Union(revocable by a minority of the population)

In 1869, Salmon P. Chase wrote the majority opinion for the Supreme Court's decision in Texas V. White. He said of the same words,

It is difficult to convey the idea of indissoluble unity more clearly than by these words.

Suffice to say, the Supreme Court's opinion matters more than unnamed "scholars".

Secession did not benefit the average southerner. Instead, it benefited the rich white southerners who owned most of the slaves. Only about one in five southern families owned a slave. The people who were deciding whether or not to secede were not thinking of the interests of the average southerner, or even the interest of the average white southerner. Instead, they were thinking about the interests of the landed white minority that was the political class, i.e., themselves. They saw Lincoln as being a slave lover, so the seceded to protect their own interests, not the those of the people at large. Keep in mind, this is before Lincoln was even inaugurated, so they had no idea what his policies would actually be.

If by,

unspeakable war crimes,

You mean that there weren't any to speak of, you're right. Atlanta was burned by Confederate soldiers trying to deny the resources of the CD to the Union Army. Sherman's Army seized resources such as food for the soldiers, and destroyed matériel like railroads and telegraphs that could be used for obviously military purposes. While there are some accounts of widespread destruction, these are mostly made by white rich southerners in the years after the war, who had an axe to grind with the union. The army did not kill noncombatants intentionally or in large numbers.

The south was not,

punished politically for generations.

The South had an outsized amount of representation in the United States Congress for years before the Civil War, and after the Civil War, they were simply cut down to size, rather than being disenfranchised.

TL;DR: you fucked with the wrong Yankee.