Your response there doesn't address the question of whether FedGov was justified in using force to end secession the first time. The Union is widely (though not universally) considered the good guys in the Civil War; that the resort to war in response to South Carolina's declaration of independence, and attempt to reduce the threat posed by Fort Sumter was correct and justified.
If, in fact, the Union's resort to war was a justified response to secession ... what is justified response to abortion.
Which is the greater injustice: secession or abortion?