It's a fine line, isn't it? Usually, my reaction in these cases is to think just how horrible it must be for the perpetrator's parents -- that TED talk by the mother of the Columbine kid just crushes me. But for them to not reach out to Gabby's family from the very beginning is inhuman.
Of course, there is a right way to do that through the appropriate intermediaries -- you can never really know what the victim's families prefer in such situations. But it's hard for me to imagine any reasonable explanation for their actions (or lack thereof). Blood is just that: a liquid substance that keeps us alive. It is not a reason to ignore another parent's pain, and that's not mutually exclusive with protecting their son's legal rights.