Well, it's not like you can just blow off the points made by "confederate apologists" (to use the words in the title). Both sides have a strong argument to make and that's why the debate still rages on.
Those who don't think the American Civil War was about slavery could quote:
A House bill passed in 1861 included the language -
“…this war is not waged upon our part…for any purpose of conquest or subjugation, nor purpose of overthrowing or interfering with the rights or established institutions of those States, but to defend and maintain the supremacy of the Constitution and to preserve the Union…”
Charles Sumner said -
"You will observe that I propose no crusade for abolition. [Emancipation] is to be presented strictly as a measure of military necessity...rather than on the grounds of philanthropy...Abolition is not to be the object of the war, but simply one of its agencies"
Abraham Lincoln's 1st Inaugural Address -
“I understand a proposed amendment to the Constitution—which amendment, however, I have not seen—has passed Congress, to the effect that the Federal Government shall never interfere with the domestic institutions of the States, including that of persons held to service….
I have no objection to its being made express and irrevocable.”
Then people who do believe it was all about slavery could quote:
South Carolina Declaration of Secession -
We affirm that these ends for which this Government was instituted have been defeated, and the Government itself has been made destructive of them by the action of the non-slaveholding States. Those States have assume the right of deciding upon the propriety of our domestic institutions; and have denied the rights of property established in fifteen of the States and recognized by the Constitution;
they have denounced as sinful the institution of slavery; they have permitted open establishment among them of societies, whose avowed object is to disturb the peace and to eloign the property of the citizens of other States. They have encouraged and assisted thousands of our slaves to leave their homes; and those who remain, have been incited by emissaries, books and pictures to servile insurrection.
For twenty-five years this agitation has been steadily increasing, until it has now secured to its aid the power of the common Government. Observing the forms of the Constitution, a sectional party has found within that Article establishing the Executive Department, the means of subverting the Constitution itself. A geographical line has been drawn across the Union,
and all the States north of that line have united in the election of a man to the high office of President of the United States, whose opinions and purposes are hostile to slavery. He is to be entrusted with the administration of the common Government, because he has declared that that "Government cannot endure permanently half slave, half free," and that the public mind must rest in the belief that slavery is in the course of ultimate extinction.
Alexander Stephens, Vice-President of the Confederacy -
"Our new government is founded upon...the great truth that the negro is not equal to the white man; that slavery - subordination to the superior race - is his natural and normal condition"
Jefferson Davis, President of the Confederacy -
"Ours is not a revolution. We are not engaged in a Quixotic fight for the rights of man; our struggle is for the inherited rights. [We left the Union] to save ourselves from a revolution that threatened to make property in slaves so insecure as to be comparatively worthless."
Alabama newspaper in 1861 wrote -
"[Lincoln's election] shows that the North intends to free the negroes and force amalgamation between them and the children of the poor men of the South. [Slaveholders] will never consent to submit to abolition rule."
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Personally,
I do believe the Civil War was fought over slavery. Whenever a student has tried to convince me that the war was fought simply because of states' rights I reply, "A state's right to do what?". But I do try to respect the other side of the argument because it's easy to find documentation to back up their side.
I'm reading a book right now,
Father Abraham, which documents sources of Lincoln's record of trying to end slavery from the time he was in the Illinois legislature. It's a pretty good read.