There's been a lot of revisionist history since the Civil War. The standard line now is that the war wasn't about slavery but states rights, and that Lincoln wasn't primarily concerned about freedom for blacks. Misterjonez and many, many others have accepted this false history. The truth is that slavery was the defining issue of the age, it was what most divided the nation and what stoked the South's anger toward the North. This is clearly stated by Southerners at the time, including in the official statement put out by South Carolina justifying their secession. I suggest everyone read that, because the only reason given is slavery, and remember that South Carolina was the first state to secede. The boilerplate response to this is to say that most southerners didn't own slaves so they must not have cared about the issue. This is patently false, The average southerner was horribly racist and was very happy to have blacks enslaved because it clearly established that they were subservient to whites. The thought of having blacks be free to live, work, shop, and go to school where ever they wanted was absolutely horrifying to southerners. That's why white southerners were so viscious to blacks after the war, installing segregation and doing everything thing they could to humiliate and terrorize freed blacks.
The claim that Lincoln didn't really want to free the slaves, he just wanted to keep the Union together is also false. He openly ran on a platform of outlawing slavery in the territories, which necessarily meant slavery in the South would be ended because eventually this policy would lead to far mor free states than slave states. The free states would then abolish slavery in the South. Everyone could see that, including Lincoln. He said explicitly that in fact:
A house divided against itself cannot stand. I believe this government cannot endure, permanently, half slave and half free. I do not expect the Union to be dissolved — I do not expect the house to fall — but I do expect it will cease to be divided. It will become all one thing or all the other. Either the opponents of slavery will arrest the further spread of it, and place it where the public mind shall rest in the belief that it is in the course of ultimate extinction; or its advocates will push it forward, till it shall become lawful in all the States, old as well as new — North as well as South.
So Lincoln knew that his stated platform would lead to the elimination of slavery, and rather than water down or change his platform to try pacify the South, he openly and aggressively campaigned on it. Thus, ending slavery must have been something very dear to him and something he was willing to risk war over. When that war came, it was far bloodier and destructive than anyone imagined it would be, so it's not surprising that Lincoln at least occasionally dreamed of ending the war without ending slavery. But that doesn't change the reality of why the war began.
Ironically, because of the revisionism, the reason for today's southerner's support of Confederate flags and monuments is quite different than their original purpose. This makes the support for them today much less odious, so I'm not totally opposed to them even though I consider their real history troubling.