Unfortunately, IMO, their "choice" of lifestyle invited tragedy into their home.
They did not PROTECT their child, instead choosing to invite strangers over to "party" on the night their child disappeared.
IMO, their actions/inactions led directly to this tragedy and their remaining children should be removed from their home.
With regard to PROTECTING one's children, I say, one strike and you're out.
I wonder what all those kids have seen?