You really need to explain what you mean because his explanation seems to make sense to me.

There doesn't have to be a problem with that explanation if you consider the possibility that what this study observed was not necessarily always the case.

Perhaps generation 1 of criminals committed crimes out of perceived necessity, but did not believe themselves to be acting morally. They failed to stress this to their children however, perhaps due to some sense of pride, and the second generation is then raised to believe that crime is normal. This second generation, unlike the first, could have an inaccurate sense of what "normal" morality is.