The actions of the slavers were not intended to bring about positive change.

No. But the partitioned system was already fraying, as the slave population began to eclipse the native white population in the south and spill over the borders into nominally "free" states up north. New York City was the largest hub of human trafficking in the nation when the war started, thanks to the Fugitive Slave Act.

By holding a unified obstructionist minority position, they could delay legal abolition indefinitely. Only by leaving the Union did they surrender their right to obstruct.

It seems much more of a correlation/causation fallacy coupled with “ends justify the means” philosophy

It should be noted that South Carolina was firing on Fort Sumtner before Buchanan was even out of office. So unless you consider "electing Lincoln" to be the mistake abolitionists made, I wouldn't consider the means questionable.

However, again, I would like to thank you for taking the time to clarify. Both here and in other comment threads.

No problem.