To clarify some points for the typically confused:

I. There can never be a "conflict of interest" in this matter. It makes no difference who makes the accusation. All that matters is whether the accusation is factual and has merit. You're probably thinking based on some personal experience in some domestic dispute, but that's largely irrelevant; the reason Mr. Policeman or whatever adult figure dismissed your accusations at that time was that they were based on your own testimony, not that they were improper by "conflict of interest" (a topic one'd be best advised to read up on, anyway).

II. There exists the doctrine of "duty of care", both in common and civil law systems. Read up on that (preferably in a law manual, not on wikipedia). Somebody with power has a duty to act equally to protect all those that need his protection. He can't pick and choose. The discussion here revolves around exactly that; Nefario has acted in some cases but not in all cases. This means he was either wrong to act at all, in which case he should make whole those harmed by his action, or otherwise that he was wrong to not act in the cases where he did not act, in which case he should make whole those harmed by his inaction. Tertium non datur as they say, there is absolutely no alternative here. Either one or the other must be true.

All the rest of the discussion is absolutely irrelevant, but obviously you're more than welcome to carry on with it.