I would start by answering that any group of human beings has faults, and since Christ came for the sinners, the Catholic Church would be expected to have it’s share of people who sin.
Then, onto what happened and why.
In the 70’s, when much of this was happening, it was commonly thought that with a little therapy treatment, perhaps a few sessions of hypnosis, these things could be addressed and the person who had perpetrated the vicious crime would be cured. This was the “expert” advice available at the time. The Church teaches forgiveness, so “knowing” as told to the church by experts, that these transgressors could go forth and sin no more, it’s my understanding that they were permitted to do just that. The problem was there apparently wasn’t adequate followed-up to ensure no other injuries were caused. I think you would find that those who made these poor decisions have great remorse for the pain and suffering they allowed to happen.
Also, in most cases, the offenses were against post-pubescent boys, young men. The correct term for the crime would be homosexual statutory rape, as these were underaged minors engaging in sex. The fact that it was an authority figure makes it even worse. But these were, on the part of the perpetrator, essentially homosexual acts, rather than pedophilia, which is with youth who are pre-pubescent.
What is being done now?
I do not know the specifics of what is / has been done with the perpetrators, but it is my understanding that as of now, if a priest is found to be guilty of engaing in inappropriate acts with a minor, they are turned over to the civil authority and defrocked.
In the meantime, each diocese throughout the USA has put into place measures to ensure that such a thing will NEVER recur. In addition to changes in the seminaries they have rolled out Parent and Child abuse awareness trainings. I know, because I was sent to a full weekend training to learn how to facilitate this program for our diocese. After making the program mandatory for all the parents of our CCD program, a similar program was offered to the Children in CCD as well. (we do not have a diocesan school).
In addition, the USCCB has an audit program in place whereby they are looking into the records of all complaints against the clergy and ensuring that each received an adequate response. There are now guidelines in place for tracking complaints so the auditors can be assured of having access to the records for followup.
All this is being done in response to a very small percentage of the clergy having this horrific problem. Your friends state they would never belong to a church that hides such a problem. I wouldn’t be so certain. Does their church have in place processes for recording all incidence of complaints? Are there third party auditors monitoring their response? There have been reports in the media of similar offenses in other religions, but the brew-ha-ha has not been as hyped as it has been against the Catholic Church.