The liberals were the southern Democrats in 1860, because they believed they had the right to own other people, treat them differently, and exploit them for free labor. That's no different than liberals today pushing for mass invasions of foreigners to exploit them for political reasons, take advantage of a cheap labor force, while discriminating against white U.S. citizens.
So far as most people are aware, that is *ALL* it says.
Not a word in people's understanding about independence, which after all, is the sole purpose of creating it.
It says 13 slave owning States had a right to secede and form a Confederacy.
But most people think it is a statement about "equality" rather than a right to independence.