As the author of the article says, it was the War Between The States. Lincoln couldn't have done much of anything without the support of the Northern States that elected him—twice.
I read that at the beginning of the war the Regular Army had a little over 16,000 men. And at First Manassas the Union forces consisted of about 35,000 men. The difference was made up by volunteers from the States. The brunt of the war was borne by volunteers from the States, not the Regular Army. (OK, later on the volunteers might have required a little “encouragement”.)
If Lincoln had had to depend on the Regular Army, without volunteers from the States and the support of those States, the South would have won in short order.
If the Northern States had acquiesced to the secession of the Southern States, what could Lincoln (who was only the President) have done about it?
He could have NOT made the call for 75,000 troops to kill their own brothers for legally seceding. Since he as only the president, and not yet king, he had to lie about what the war effort was in order to get volunteers to kill their kin down South.