Okay, we seem to be having trouble communicating.
Your claim was that “states” were treated differently.
The Republican party platform said nothing about treating states differently, but rather about whether slavery would be allowed to expand into the territories, where the federal government, not the states, had authority.
Slavery had previously been outlawed, with minimal complaint, in some of the territories for decades until repealed at southern assistance. Yet the reinstitution (and possibly expansion) of this previous policy in your mind was somehow an example of treating states differently that justified secession and war?
Lincoln’s remarks about a house divided being unable to stand is actually a quote from the Bible. As he said at the time, if you wanted to argue the principle, you needed to take it up with a higher authority than him.