I think that deamonizing the family is some people's way of fooling themselves into thinking it can't happen to them.
The JBR's parents dressed her up as a slut and taught her to strut for grown men, the Van-Damns were swingers who's 'alternative' lifestyle opened the door to their child's abductor. We hear about their kids missing and don't don't feel to threatened because they are not like us.
They don't want to think that a strong, healthy, traditional family would have this horror happen to them, so they look for the slightest sign of something odd to exagerate and deamonize them with. Then they can go on thinking they are safe.
The other alternative is that here on FR we use the same techniques for trying to get to the truth in these matters that we do on all other matters. And, that we believe that one of the Ramsey's family did it (which I think is obvious). And, we think that the VD's horror would not have happened had they not had wild orgies in their house, and not broadcast their sexuality such that a perverted neighbor would have become obsessed with them.
Very good point; worth repeating.