It is misleading people. The purpose of the Civil War was not to free the slaves. It was to stop renegade states from becoming an independent nation.
The southern states were prosperous and the north was hording the tax revenue from that prosperity. Taxation but little representation.
In terms of an historical timeline, this may or may not be the case; I'm not sure I want to get into that debate. Nevertheless, the history of American wars, most if not all of the time, often includes discerning a moral justification that existed before the war, while in the midst of fighting the war.
For example, we began fighting the British in 1775, and it wasn't because we wanted to be independent, or because we wanted to establish a Lockean tripartite government; the independence idea grew out of the war, though it had been percolating before the war, and the form of government, and the negative rights that were to limit the government, grew out of the victory, though they also had been percolating before and during the war.
By the same token, we entered WWII because the Japanese attacked us, and our first reaction was simply to get back at Japan; it isn't until later, in the middle of the war, that we began thinking in terms, not simply of forcing Japan to surrender, but in exporting American ideals to Japan, though such ideals had been percolating beforehand--cf. Captain Cassidy's speech in the 1943 movie Destination Tokyo, about how the war's purpose was putting Japanese children on roller skates instead of letting them be taught to die for the Emperor.
We find similar during-the-fact percolations of moral justification in the Mexican-American and Spanish-American wars: in the latter, for example, bringing American ideals to Cuba and the Philippines (with moderate success in the Philippines, less so in Cuba).
It may be something in the American psyche that desires a moral justification, because, liberal claptrap to the contrary, we are not warmongerers, we are not imperialists, and if we have to fight a war, we want it to mean something more than, "We can kill more of you than you can kill of us."
Exactly.
Lincoln said if he could “preserve the Union” without freeing a single slave, he would do so.
Just added some context.