Freeing the slaves was not "injustice."
Quite the opposite.
Freeing the slaves was not the reason Lincln invaded the South. If Lincoln and the yankees had been so self-righteous about freeing the slaves, why didn't they emancipate all slaves north of the Mason-Dixon line before beginning their illegal and unjustified war against the Confederacy? That would have provided a wee bit of credibility to the 'war to end slavery' crap that you've swallowed.
Have you ever read the Emancipation Proclamation?
It was nothing but a political tool designed to provoke a general uprising in the Confederate States of America by slaves, which was actually damned reckless on Lincoln's part because an uprising may have resulted in the wholesale slaughter of tens of thousands of slaves.
Of course, disHonest Abe had probably figured that the slaughter of scores of slaves would have benefited his political agenda and aspirations, as well, so either way was fine with him.
By injustice I mean the invasion of a sovereign nation, the waging or war on women and children and the subsequent military occupation.
If freeing slaves is justification for military invasion, why aren't we invading Africa, Asia and other countries that are known by our State Department to permit slavery?