How does Mxolisi's offence bring on a derogatory meaning to the term mother

It may make it seem as though Mandisa (Mxolisi's mother) took no interest in teaching her son the difference between right and wrong. One might say that it is because of Mandisa's inadequate appeal to raise her child as to not to do such things, hence it could influence the term "mother" as a rather derogatory one.