While running for President, Abraham Lincoln would tell northerners that they were not morally superior to southernors, although the northernors were opposed to slavery, and the southernors supported slavery. What distinguished him from other abolitionists was his appeal to the virtues he saw in the southernors, in seeking to dissuade them of slavery. For example, had not they voted along with the northenors to abolish the import of slaves from foreign lands? Had they not voted on a compromise that would prevent the expansion of slavery to free states? If a southernor sought to justify slavery on grounds that the more intelligent had a right to make the less intelligent subordinate, he would ask how the southernor would feel if someone claimed to be more intelligent than he. Would he submit to being enslaved? A southernor would tell him that slavery was a necessity because of scarcity of labor, and his reply was not that the southernor was exploitng and oppressing the slave, but that free black was more productive than the slave. Essentially, Lincoln sought to defeat slavery without challenging the self-esteem and dignity of the southernor.

Attitudes towards slavery were evolving during the 18th century. In his younger years, Benjamin Franklin owned three slaves while living in Philadelphia. Just before his death, at a time when he was closely associated with Quakers, he wrote a satire condemning slavery. Similarly there is reason to suspect that the Quakers of Greensboro, NC, such as Swaim, and Philadelphia, PA, such as Benjamin Rush, and perhaps even Benjamin Franklin, influenced the Rev. David Caldwell.

In North Carolina, white hostility and cruelty towards slaves became more prevalent as their population ballooned. Whereas the Presbyterian Synod to which Rev. Caldwell belonged favored teaching the blacks to read, within a decade after his death North Carolina passed a law prohibiting such teaching.

There was virtually no statutory difference between
free-blacks and whites for much of Rev. David Caldwell's lifetime. Free blacks were allowed to vote. Either shortly before or after his death, the free blacks were disenfranchised in North Carolina.

In the ante-bellum South, the black slaves were often allowed to have possession of rifles so that they could hunt. The master would have to get a permit from local officials. This implies a relationship of trust and confidence.

I think it is fair to say that there was a spectrum: kindness to harshness, trust to negrophobic, nurturing to bestiality, and we have reason to surmise that the Reverend Caldwell was one of the kinder and more benign masters.

The subject of slavery in North Carolina is explored more thoroughly in various publications available from the State of North Carolina:

North Carolina's African American Heritage
A History of African Americans in North Carolina
The Black Experience in Revolutionary North Carolina
James City: A Black Community in North Carolina, 1863-1900
Recollections of My Slavery Days

http://www.ah.dcr.state.nc.us/sections/hp/catalog/titles.htm#AfricanAmerican