How did proponents and opponents of slavery use similar concepts in their arguments?

It's interesting that both supporters and opponents of slavery drew upon Christianity to back up their arguments. For abolitionists, their opposition to slavery was nothing less than a moral crusade, a crusade based on the Christian principle of universal brotherhood. It's notable that many of the leading lights in the abolitionist movement were clergymen, and they sought to infuse the campaign to abolish slavery with a distinctively Christian flavor. In a society where just about everyone believed in God, it was important for abolitionists to convince people that they had divine sanction for what they were proposing.
For their part, supporters of slavery were equally adamant that they had God on their side. They pointed to numerous passages in scripture which they claimed endorsed slavery. To the advocates of the peculiar institution, slavery was part of God's plan. If certain races were slaves, they argued, it was entirely due to the will of God, and no man had the right to challenge it.