The retort's claim that the nuclear family is a relatively modern concept formed in response to 19th century economic and societal changes is accurate, but is missing the point of the essay. The essay wasn't about the origins of or timeline of the nuclear family; it was about the implications of its unraveling. To say that there are often survivors when a nuclear family unravels is also accurate, but doesn't change the fact that there are often no survivors when this happens. There can be emotional, mental and relational casualties in these situations, even if the children remain intact.
Additionally, the research presented in the retort only speaks to the success of children who come from broken homes. The original essay wasn't about academic success or lack thereof; it was more about the emotional and mental effects on family members. To say that success is a measure of survival of a nuclear family unit unraveling is UrRong.
Nikhil's original essay brings to light an important point: just because a nuclear family unit is designed to stay together, it doesn't mean it will always stay that way. Life can result in unexpected changes that can cause any unit to unravel and leave emotional, relational and mental casualties in its wake. To deny the reality of this statement, or to put too much emphasis on the potential for success post-unraveling, is to miss his original point completely. And that's UrRong!