How are Nadine Gordimer’s political beliefs reflected in the story "Once Upon a Time"?

Nadine Gordimer expresses a strong opposition to the apartheid of South Africa in her short story "Once Upon a Time."  In this story, structured like a fairy tale, Gordimer shows the detrimental effects of apartheid on those at the top of the power structure.  Gordimer's story describes a family living in a community in which they fear the invasion of the "other."  To keep their possessions safe, they and their neighborhoods put up neighborhood signs to discourage intruders with words such as "You have been warned," purchase electronic security systems, build higher fences, and install vise-like contraptions over these fences.  
All these precautions ironically result in a less safe and less attractive community.  With their tall fences, the neighborhood begins to look like a concentration camp. To protect themselves, they imprison themselves. The alarm system provides cover for thieves.  The Dragon Tooth contraption results in the death of their son.  Through this story, Gordimer shows quite clearly what an apartheid system does to those who continue to enforce it. 
But we also see more socialistic tendencies in the story.  The story itself is a frame story.  The frame is the author's writing a children's story when she is awakened and frightened by a noise she heard.  She finds out that the noise was caused by the fact that her house was built over an underground mine that had perhaps in earlier years collapsed upon and interred the workers down below.  This small detail is important because it can serve as a metaphor for Gordimer's political leanings.  The foundation of the house is shaky (like the apartheid government), and its first victims are those down below or the lower class, but eventually the tremors that have such devastating effects on the lower class will result in the collapse of the entire household or government.  In other words, when one segment of society keeps getting poorer while another segment of society keeps increasing their wealth and possessions, that society is no longer stable and will eventually fall.  A vastly uneven distribution of wealth negatively affects the entire society.