[Wow, I agree factually, with everything you wrote. Imagine that.
Union troops did invade the South and the South resisted the invasion. That's the southern position. But people like Andrew Jackson had already existed by that time, and the US was long into it's mission to create one nation spanning the continent. Andrew Jackson raised regiments to invade Florida and kill the Spanish, and the Spanish defended against the killing. He captured military posts, and also arrested and killed British subjects. Then the US took over and your ancestors defended it again a generation later.
The justifications for secession all include the word slavery in great quantity, and those are their word, not mine or yours. Do a CTRL "F" on them, and see for yourself.
Legal Justification of the South in Secession
You missed my point entirely.
You can discuss and argue all day long about the reasons for secession and if they were justified or not.
I personally think that the real energy in the Republicans resisting slavery was so that they could get more political power by having non slave states into the expansion into the west. Politics of power, plain and simple. You see it today. You have to remember than nobody, even Lincoln, was advocating ending slavery in the US in 1861. There were people that were against slavery but there was no serious political movement, led by the Republicans, to put an immediate end to it.
However, all that political crap aside, the point that you missed is that the hundreds of thousands of Confederate soldiers did not fight to protect slavery or even secession. They fought to protect their homeland from the invasion that Lincoln initiated. That was the war.
The thing that most Americans have a very difficult time doing is separating the reasons for the secession from the reasons of the war.
Lincoln did not start the war and invade the South to free the slaves. He didn't even free the slaves in the US or parts of the occupied South. He invaded the South to "preserve the Union" (his words). The people in the South fought against the invasion, which was the proper and courageous thing to do.
The thing that we have to do nowadays is face the moral question of was it right to kill Americans that wanted the freedom of their own self determination.
I would never want to kill somebody because they did not want to part of the US anymore. That would be immoral, wouldn't it?
It Texas seceded from the Union nowadays would you think it was justified to kill them for it? I wouldn't it. I would want them to be free if that was their wishes.