Hi there!
What were their fears and what was Lincoln's viewpoint? Lincoln's views on slavery, race equality, and African American colonization are often intermixed. Lincoln expressed his then view that he believed whites were superior to blacks. Lincoln stated he was against miscegenation and allowing blacks to serve as jurors. I'd imagined that his advisors feared about how the southerners would take it and how they'd react knowing the possible consequences.
Hope this helps!
-WolfieWolfFromSketch