If Britain and France had allowed Germany to conquer Poland, there wouldn't have been a war in 1939.
If the colonies had submitted to George III, there wouldn't have been a war in 1775.
If the US had allowed Iraq to keep Kuwait in 1989, there wouldn't have been a war.
The whole argument was about whether the South had the right to secede. Of course if they had not been opposed, there would have been no war.
The way I look at it, the right of secession is still an interesting subject. If the states still have that right, which I believe they do, in theory, if Hillary wins the next election, the red states can just secede....:)
And if they did indeed have the right of secession, then Lincoln was wrong.