They do not see that their own participation in a racist society perpetuates societal unrest and poisons their own sense of morality and ability to reason. They sabotage themselves the little boy dies not because of some faceless intruder but rather because of the couple's conviction that the Black people in the area are dangerous. They allow this fear to become an obsession to the extent that they render their house and property ugly, inhospitable, and, eventually, deadly. The husband and wife are concerned about the rash of burglaries and decide that they must shore up their home and possessions against the perceived danger of the shiftless Black itinerants coming around their neighborhood. The while people see themselves as virtuous and beset-upon they must keep their possessions and their loved ones set apart from the strange and hostile outsider. The white people in this story evince that deeply held fear of the "Other": Black people whom they believed to be trying to take their things and cause them harm. In the era of apartheid, which featured rigid separation of the races based on the complete codification of racial difference, white people and Black people had proscribed roles, areas, and stations, all of which were fundamentally different from each other. They think they are not racist because they aren't openly aggressive about it, but they are fundamentally shaped by a sense of their own white supremacy such that every comment, every thought, and every action in the story is about keeping themselves safe from the dangerous, rapacious, threatening Other. All of these examples contribute to the subtle racism that the couple possesses.
The couple comforts themselves that they are not racist because their sign has a silhouette of a person who could be either white or Black. The housemaid criticizes other members of her race in order to set herself apart. The "wise old witch" warns her son and daughter-in-law "not to take anyone off the street." The housemaid and gardener are Black, yes, but they are "trusted" and "highly recommended," which contrasts with all of the others.
None of the characters says anything overtly racist in the story, but racism is still there, simmering just below-and, occasionally, just above-the surface.
The husband and wife's inability, or lack of desire, to understand the plight of the Black people in their region and how members of their own white racial group were the ones who created this system of racial separation and concomitant unrest, despair, and deprivation encapsulates the brutal unfairness of apartheid in South Africa. Outside the neighborhood are riots by "people of another color" who are not allowed into the husband and wife's neighborhood unless they are "trusted." Those other people eventually do come into the neighborhood as outside events like "police and soldiers and tear-gas and guns.buses were being burned, cars stoned, and schoolchildren shot by the police in those quarters out of sight and hearing of the suburb" and widespread unemployment lead to the uprooting of a population.