Though it has been stated that Lee has called slavery a moral and political evil, he still was a slave owner, as well as a Southerner; he did not advocate for the abolition of slavery, and believed slavery was a necessary evil to help slaves survive (many Southern slave-owners had a paternalistic view of the relationship between a slave and his/her master).

There are many interpretations over the cause of the Civil War, but the general consensus is that slavery was in fact the primary contribution to the war. A good amount Northern politicians wanted to gradually end the institution of slavery, and especially wanted to prevent slavery from spreading westward in the United States. Southerners, on the other hand, believe it was a God-given and constitutionally protected right to have slaves. And sectionalism was very prevalent between the North and the South from the early 1800s leading up to the Civil War, and the issue of slavery heavily contributed to sectionalism. Robert E. Lee identified as a Southern (a Virginian first and foremost), and ultimately chose to follow his home state out of the Union, and fight for it.