Through these faults of the destroyers of the family, which cause the mixing of social classes, the age-old duties of caste and of family are wiped out.
Explanation
Arjuna continues his argument for why he should not fight his own relatives. He says that the wrongs (doṣa) of those who destroy a family lead to the mixing of social classes (varṇasaṅkara), and this in turn wipes out the long-standing duties (dharma) of both caste or community (jāti-dharma) and family (kula-dharma). These terms reflect the social order as Arjuna understood it, and Krishna goes on to challenge his reasoning in the next chapter.