"An Abandoned Bundle" is all about shock value.  The line "an infant dumped on a rubbish heap" is meant to shock and horrify, especially when this line follows an equally disturbing description of the baby's "mutilated corpse."  As a mother, I was hardly able to stomach this poem due to its graphic images of death, especially when that death is an infant.  The connotation of "dumped" and "rubbish" suggests that the baby is little more than garbage, an idea that it completely offensive.  Mtshali draws readers' attention to the incredibly sensitive social issue of apartheid by showcasing the bleakest, most desperate situation--baby abandonment.