What is the most dominant cultural theme in "Once Upon a Time" by Nadine Gordimer?

I think that the most culturally relevant theme to come
out of Gordimer's short story has to be the fear of "the other."  The strength of this
story is that its context is apartheid South Africa, a system that was predicated upon
containment of "the other."  White South Africa lived in the Apartheid configuration
because it restricted the movement and opportunities of Black South Africans.  This
helped to establish the idea of "the other" being kept at bay.  The establishment of
gated communities, White flight from the urban centers, the development of suburbs and
the basic idea that all that is bad and wrong with the world can be contained to a
particular area or group of people is brought out in the story.  The family's desire to
protect their interests is done so in a manner that lets fear of "the other" run wild. 
The family is not overtly racist (as it points out in the story with the sign of
"trespassers beware"), but does operate out of a position of fear and the inability to
appropriate "the other" into their world is what causes them to be more inwardly drawn,
leading to the death of their child and the valley of despair.  Impossible to divorce
from the South African context, Gordimer might be suggesting that the fear of "the
other" in South African politics and social organization can only result in more despair
and pain, as opposed to anything redemptive or productive.