What is wrong with the Catholic clergy, and what is wrong with the hierarchy? I know that in any randomly chosen population of men, there is bound to be a certain percentage of pedophiles, but the problem appears to be so epidemic among priests that it suggests there is some kind of causal mechanism at work here.

Does becoming a priest make you more likely to be a pedophile? Or do pedophiles tend to be attracted to the priesthood? And it seems to be an international problem, not just in one country or in one ethnic group. Either way, it's pretty scary.

And what about the vast majority of priests who are not pedophiles, a majority of them who I have no doubt take their moral responsibilities very seriously? How could they have not been aware of this, and if they were, why didn't they do something about it? I simply cannot comprehend how there can be so many evil priests, and how so many good ones could just look the other way.

This is not just an activity that violates their religious principles; in historical times priests were often known to have mistresses, even wives and families, or to occasionally dally with prostitutes. This goes much further, this is behavior that is even condemned by secular society in general as hideous and grotesque.