On what grounds did white South Africans justify/rationalize separating black ethnic groups?

In italy, the distance between milan in the north and palermo,sicily, in the south is about 550 miles. in the united states, the distance betweenboston, massachusetts, and savannah, georgia, is about 900 miles. do you think the american revolutionaries of 1776 in the 13 colonies faced some of the same challenges as the patriots who struggled for italian unity in the 1860s?