You are assuming that your opinion of what's right is right. I respectfully submit that it's not that easy.
To be fair, the it's a discussion forum, and we are discussing each others opinion. So, yeah, IMO my opinion of what is right is correct.
But on a less superficial level, we each judge the world around us based on our personal value system, as influenced by religion, morals, learned mores and the like. Some cultural relativism is a good thing. If someone does something different with you and it does no one direct harm, then it's probably best to not interfere, and let them do their thing. That attitude can go to far though. If people are getting hurt because someone's beliefs are different, then it's probably time to not pretend that those beliefs are "OK" (at a minimum).
I understand that the priest in question may find themselves in a moral dilemma weighing their interpretation of gods law, church doctrine, and secular law on deciding whether to protect children. I however have no such moral dilemma. Hurting children is wrong. Allowing children to be hurt by your inaction is wrong. My gods require no dithering on this subject. So I can pretty safely say that a person, priest or not, that doesn't stop child abuse (or prevent potential child abuse) that they know of is immoral. A church that requires this of their clergy is an immoral institution. If, as Ron alluded to, the church were to stop it outside the secular authorities I might reconsider, but we have ample evidence that churches (and other organizations, to be fair) don't do that. So we are back where we started: they need to report it to someone that can stop it.
In this case the priest and the LDS did the right thing, and protected children. I'm glad, and I hope they prevail in court, but even if they don't and have to pay something, they were correct.
In the spirit of discussion I am going to circle back to your comment on my opinion of right (pretty aggressively, I admit):
OK, maybe I am wrong in this hypothetical. On one side, a clergy breaks the seal, involves authorities, and removes an abuser from contact with children. On the other side, the clergy maintains silence, (presumably) councils the abuser to help them stop and earn divine forgiveness, and sends them back into the situation they abused children in.
Choice A: Abuser is removed, child sees justice happen, child learns that adults will protect them.
Choice B: Abuser may earn divine forgiveness but faces no immediate consequences for their crime, child sees no Justice, child is at risk for future abuse.
I repeat my first comment: How is this a question?