By the mid-1800s southern defenders of slavery argued that the institution was not exploitive; it was because blacks were taught disciplined work and were saved by christianity

The answer is civilizing. In the midst of the mid-1800s, southern defenders of slavery discussed that the organization was not oppressive; it was civilizing for the reason that blacks or the African Americans were being trained to be disciplined workers and being disciplined at work and they were also saved by Christianity.