This is as much of a distortion of history as you lost causers claiming the south didn’t rebel to protect slavery. You must be very proud that your using the same tactics the left is using.
Claiming that slavery needed to be "protected" from the Union is the distortion. Not only was slavery protected by the US Constitution in Article IV, section 2, so too did Lincoln and his allies attempt to pass a constitutional amendment protecting it even further.
You may have missed it, but slavery was legal in the Union, and would have continued to be legal indefinitely if no efforts to leave had been made.
Therefore, it wasn't about slavery, it was about leaving.