Understand, however, that I am opposing the very idea of the ends justifying the means -- which is why I stick so closely to my guns on Lincoln. With the information available to him at the time, and the choice of peaceful secession or Civil War before him, Lincoln chose to marshal the forces of the North (which had a population of 22 million) against the forces of the South (which had a population of 9 million). And that doesn't tell the whole story of the power disparity between North and South -- it was probably twice as great as the population differential indicates due to the North's greater financial wealth and manufacturing capabilities.
It's really, really hard to paint Lincoln's choice, in that light, as anything but abject tyranny. If he had loudly declared, early and often, that his war was to abolish slavery in the Americas I would have had much, much greater respect for his ideas. I might have even agreed with his rationale and chosen course -- but he was ADAMANT throughout his time as US President that slavery was not the purpose for his drafting an army and suspending habeas corpus. How would we feel about Obama selectively ignoring habeas corpus when it came to dealing with his political opponents? That's right: he'd be correctly considered a tyrant.
The Founders were committed to a balanced system where the State and Federal Governments could push back and forth with roughly equal power, if enough States got behind a given issue. When this system was destroyed in the Civil War (and that's what happened: it was functionally abolished, with only vestigial components remaining -- oddly enough, just like slavery) it destroyed the first, and possibly last, example of humans attempting to live under this type of multi-tiered, self-balancing government. The whole point of the balance of power between the States and the Feds was to keep the Fed from growing large enough to override the States on the majority of issues -- it was not to provide for a sturdy Federal Government by keeping the States lock-step together under coercive means. The States, with their individual social attitudes and economic idnetities, were the foundation and therefore the most important component of the Union; the Fed was the mechanism for common good to be served in ways that were perhaps beyond the States' individual abilities.
Now let me propose a scenario which, while considerably less likely than one which resembles our current history, shows a different development path for the world. Let's say that Lincoln permitted the States to secede, and then let's say that a few decades after secession slavery was abolished due to some technological improvements in the cotton industry (as of the Civil War, cotton was literally the only crop in American which was profitable with slave labor. Everything else had advanced, technologically, to the point where it was cheaper for farmers and plantation owners to employ fewer skilled laborers and greater numbers of livestock, such as horses and oxen, than it was to employ droves of cheaper slave labor)
Let us also imagine the North and South eventually coming together in some form or another, either via outright reconciliation and reunification of the North and South, or via strong economic treaties which proved every bit as strong as the original colonial ties had been. And let us suppose that the rest of the world took notice of this grand display of diplomacy, which could have ONLY been made possible by virtue of the Founders' original government alignment (balance of power between Fed and State, with strong emphasis on peaceful resolutions rather than military ones). I ask you to imagine, if you will, how brightly this beacon might have shone for the rest of the world -- and just how desperate the citizens of other countries would have been to reform their own nations into something resembling the American System, or to abandon their home countries altogether in search of a better life in America.
And I'll even suggest that, as complex as human sociology is, it is not unreasonable to think that the World Wars might never have happened if another fifty years of American peace and harmonious growth been maintained. Perhaps Germany would never have permitted fascists to assume power; perhaps communism would have never taken root in Central Asia; and perhaps economic power would have even MORE greatly consolidated within the USA's borders with the increased influx of skilled and capable entrepreneurs who flooded American shores.
You might be scoffing, and if you are I will direct you to the fact that after the USA was formed and its formation was protected from immediate harm, essentially every government in the Western World adopted significant components of the Decleration of Independence, the Constitution, and the other fundamental documents which created the framework upon which America was built. How much MORE influence might the American system have had on the world if it had shown that even something as divisive as the period and events leading up to the 1860's could not prompt people living in this system of government to take up arms against each other? Of course this is idealistic talk, but is it any more idealistic than a bunch of colonists declaring they were sick of taxation without representation and were ready to fight one of the most powerful nations on the face of the Earth to secure freedom -- or die trying?
The only possible way the world's history could have been more positively tilted than it has been, in my opinion, is if America had done a better job of leading the world's people by example, and the first catastrophic misstep in American history was the Civil War. The Civil War was a terrifying prospect for people who didn't live in the USA but were considering immigrating to the Americas, and don't think for a minute that the Civil War's ensuing rivers of blood weren't a major talking point for countries whose best and brightest were contemplating striking out in the so-called Wild Frontier of the Americas.
My point isn't to suggest that the above is a likely outcome; I have no idea how likely it would have been. But I can say, without reservation, that during its first ~century of existence America broke every sociological rule that had been laid down by its forebears and it flourished as a result of, not in spite of, the breaking of those rules. Lincoln's subjugation of the South was a major step backward from the trail his predecessors had collectively blazed, and that war was more akin to the feudal suppression wars of old Europe and ancient Asia than it was of the Founders' ideals -- and, by extension, what America had stood for not only to her own citizens, but to the rest of the world's people, was forever changed for the worse. This is independent of the fact that slaves were freed, the USA stabilized the 20th century during humanity's most explosive period of technological innovation, and that the USA is still considered a global leader on many issues including human rights.
To me, the ends do not justify the means. To someone who thinks that they do, I can understand and even co-sign the logic behind a position supporting Lincoln. But his was an act of tyrrany, pure and simple, no matter what good might have come as a result of that tyranny.
The damage which Lincoln inflicted on the USA's legacy was irreparable, and I have seen (and even made!) certain arguments that tyrannical acts by leaders of 'beacon-esque' countries like the USA are worse, for the world as a whole and likely for the specific country in question, than the acts of a ~middling country's leader doing likewise. Lincoln's Civil War was more akin to a brutal suppression, enacted by a dictator of a third world country, than it was to the tempered act of the Free World's most eminent statesman. To me, that makes it many times worse than when someone like Saddam Hussein engages in ethnic cleansing in Iraq. The cost of human life may be identical, and the economic impacts might even be the same, but the same act corodes and tarnishes the symbol of America far more damagingly than it does the reputation of a lower-tier country. The world's beacon of hope dims with every attack against it, and the impact of that dimming cannot, in my mind, be underestimated.