I'm not defending anything or anyone here, and people commit heinous unthinkable acts from all kinds of jealousy, but that level of sadism doesn't have to be victim specific in emotion. Rather, it's probable that there was no emotion whatsoever on the part of DW. DW's history of violence, threats and sadism supports the torturing of this child.
Now, I'm defending JW. Nowhere in JW's history is there any indication that I've seen (I've not seen everything, I'm sure) that he's violent, unreasonable, unkind, had trouble with others, threaten anyone, abuse drugs or alcohol, steal things, rob people, get arrested for anything, etc. If he has anything to do with this, it would have seem to be completely out of the blue. I know there is a first time for all kinds of things, but there's usually some indication of mental or emotional disturbance. People have posted that nobody in SM is coming out to defend him, but I haven't seen any of the usual nutters who come out of the woodwork with anything negative, either.
Just saying that I think PS was used as a tool / leverage to manipulate the others. If DW is a psychopath - it seems like he is- aren't they usually pretty intelligent? He would have figured that out that normal parents would and do lay down their lives for their children with zero hesitation, and someone torturing your child would make you do anything to stop it.
It feels so hard and cold to say that a child was used as a means to an end, but it happens and it doesn't have to be personal at all. To a psychopath.