"Content" isn't exactly the word I would use here, though you're not completely wrong. Per Scott v Sandford neither Congress nor the President had any authority under the Constitution to limit or regulate slavery. That was the law. Lincoln was a lawyer, not another John Brown.

His contribution was in stopping at nothing to preserve the Union. Without it, with the south seceding, plans were afoot to reinstitute the African slave trade & extend slavery into the Caribbean.

To speak of abolition, equal rights, suffrage for black voters, etc. is all meaningless flummery unless the Union is kept intact. And this might be where some people stumble on the war & its causes, for the south seceded to preserve slavery, but the north's reason for going to war primarily was to preserve the Union. It had to be.

I don't know where Mr. Daniel gets the idea Lincoln owned slaves not freed after the war ... technically he didn't even survive the war because Johnston was still unsurrendered when he was murdered. He certainly owned no slaves.

Finally, credit is seldom given by antiracist writers today to Lincoln's efforts to pass the 13th amendment through the House, which guaranteed its adoption into the Constitution.