necessary evil
It appears that the pamphlet "The African Slave Trade" tends to have the most favorable view of the slave trade, as it argues for the economic benefits and justifications of slavery.
By 1861, it is clear that most people in the Northern non slave US States believe that slavery is immoral. By the same year many not most, of the people in the Southern States believe that slavery is not immoral.
Individuals in the antebellum South, particularly slave owners, plantation owners, and advocates of states' rights and white supremacy, would most likely have a pro-slavery point of view. They believed in the economic benefits of slavery, the preservation of their way of life, and the superiority of the white race.
Most Northern states outlawed slavery
Lincoln wanted to abolish slavery, and to forgive the states that were defeated.
Like most Northerners, Lincoln had been willing to tolerate slavery in its traditional heartlands, but did not like the prospect of an extended slave-empire. When he issued his Emancipation Proclamation, it was for strictly tactical reasons, though no doubt it also caused some Northerners to re-define their views on the slave system.
It was a Northern State that was pro slavery and anti Confederacy. It did not view the civil war as a slave issue. It considered the civil war a states rights issue.
A slave's view of slavery would likely be one of oppression, loss of freedom, and degradation. Slavery strips individuals of their basic human rights and autonomy, leading to a sense of helplessness and despair. It is a system that perpetuates inequality and perpetuates generational trauma.
The north was against slavery, and the south favored it.
Southern slave owners generally viewed slavery as essential to their economic prosperity, social hierarchy, and way of life. They believed that slavery was a natural and necessary institution, and that it provided the foundation for the region's agricultural economy. Many slave owners also used racism to justify the subjugation of African slaves, considering them inferior beings who needed to be controlled and guided.
Slave holders wanted poor whites to view slavery as necessary for the economy and society in order to prevent them from organizing against the institution of slavery. By instilling a sense of superiority in poor whites over enslaved individuals, slave holders sought to maintain social order and divide potential sources of resistance. Additionally, by convincing poor whites that their own livelihoods were tied to the existence of slavery, slave holders aimed to ensure their continued support for the system.
Because it would allow new slave-states, if the people of any state voted for it.