Rick asks the fundamental questions.
What intrinsic deterrents did the abusers overcome to begin their sordid behaviors? What spiritual blindness did the bishop have to see this a clinical problem? These are the core questions. They are both spiritual. Enforcement both internal and external to the Church are certainly factors, but essentially they are not intrinsic. What happens to a man spiritually that would incline him to take advantage of minors to satisfy his own lusts? If we can answer this we have the most important (but not the only) solution to the problem of clerical sex abuse.
The abusers, as far as I can tell from the documents, range from narcissists to psychopaths. They have no feeling for the pain, sometimes literal, physical pain, they are inflicting on the victims. I don’t think that some of the abuser were even believers; they were atheists, who saw the priesthood as an easy life that gave them access to victims and which protected them from prosecution. Those who were not atheists often pickled their brains in alcohol (and more recently, drugs); alcohol does bad things to the judgment center of the brain.
How did these extreme narcissists and psychopaths and atheists get themselves ordained? There was a gross failure of discernment in the seminary, even when the bishops and seminary officials had plenty of warning signs (read the murder-suicide case of Ryan Erickson).
The bishops and the officials in the Vatican also suffered from narcissism and a lack of empathy. In any hierarchy, business or ecclesiastical, those people who are cold-hearted and are willing to step on other people on their way to the top rise to positions of authority. The narcissism becomes a culture, clericalism.
The phenomena are both spiritual and psychological. How to keep narcissists out of positions of authority? I wish there were an easy answer; but conditions in the church, chiefly clericalism, both attracted and enabled narcissists and psychopaths. The case of Maciel is probably one of the most disturbing in the history of the Church. Benedict rightly called the psychopathic Maciel “a false prophet” – but John Paul praised and enabled him.