Confederates were "the attacking side" and they certainly did intend to defend slavery.
The Union in defending itself also advanced the cause of emancipation, abolition and full citizenship for African-Americans.
Regardless of how much you spin it otherwise, those remain facts of history.
The North Attacked first. Both in terms of sending a war fleet to engage the Confederate forces around Sumter, and in the fact of firing the first gun shots at members of the Florida Militia at Fort Pickens.
“The Union in defending itself also advanced the cause of emancipation, abolition and full citizenship for African-Americans.”
That is an interesting comment.
Tell me more about how the slave state of Maryland attacked the slave state of Virginia.
And how the slave state of Delaware attacked the slave state of North Carolina.
And how the slave state of Kentucky attacked the slave state of Tennessee.
And how the slave state of Missouri attacked the slave state of Arkansas.
And how the slave state of West Virginia . . .
Were the slave states attacking the other slave states to protect slavery?
Or were the slave states attacking other slave states to stop the other slave states from stopping them from freeing their slaves?