Where you and the writer from the London Spectator both err in common is that you overlook the fact that Lincoln had no authority to abolish Slavery in the Union. Can you really say, with a straight face, that “Lincoln didn’t want to stop slavery in loyal states”?
And Lincoln's argument in raising an army was that the seceded states were still in the Union.
He maintained this throughout the war. It was his legal justification for doing what he did.
If he had no power to abolish slavery in the Union, how can he have power to abolish it in the Southern states which he maintained were still in the Union?
Can you really say, with a straight face, that “Lincoln didn’t want to stop slavery in loyal states”?
He didn't want it as badly as he did control of the Southern states.
He promoted the passage of the Corwin Amendment, didn't he?
I think he probably didn't like slavery, though i've read claims that he was in reality indifferent to it, but knew he had to articulate this position for political reasons.