In my opinion, the moment the WT/elders take on the responsibility of "watching" these known pedophiles they become responsible for every child in that congregation!
Now, if they went to each parent and warned them against this pedophile and the parents ignored that warning and allowed their child to be around such pedophile...then, you can blame the parent.
How can we protect our children if we don't know who to protect them from??
Yes, we all know to teach our children about good touch, bad touch. We all know to check out the sex offender lists in our neighborhoods. But we Don't know what brother elder knows about what brother pedophile tells him in the back room.