Slavery was a side issue, a mere pretext.

If it were not convenient to hand, some other excuse would be used.

Here in Charleston, the first home of secession, among people who were charming in manner and kind, the feeling was very strong upon him.
He left the house after luncheon, and, following Madame Delaunay's instructions, came very quickly to St.Andrew's hall in Broad street, where five days before, the Legislature of South Carolina, after adjourning from Columbia, had passed the ordinance of secession.
Two soldiers in the Palmetto uniform were on guard, but they quickly let him pass when he showed his letters to Senator Yancey.

Inside, a young man, a boy, in fact, not more than a year older than himself, met him.
He was slender, dark and tall, dressed precisely, and his manner had that easy grace which, as Harry had noticed already, seemed to be the characteristic of Charleston.
"My name is Arthur St.Clair," he said, "and I'm a sort of improvised secretary for our leaders who are in council here." "Mine," said Harry, "is Henry Kenton.

I'm a son of Colonel George Kenton, of Kentucky, late a colonel in the United States Army, and I've come with important messages from him, Senator Culver and other Southern leaders in Kentucky." "Then you will be truly welcome.