There is another child sexual abuse crisis in the Catholic Church. A crisis other than that of clergy and religious abusing minors. A crisis no one is talking about.
Suppose you are sitting at Mass with several hundred other laypersons, and you begin to wonder if the priest saying Mass is a child abuser. In all likelihood, he is not. The percentage of priests who abuse is low, almost certainly in the single digits. But what about the other adults in the room? What percentage of adult Catholic laypersons, who attend Mass, are also child abusers? Child sexual abuse (CSA) is so widespread in modern society that any room with a few hundred adult men contains some child abusers.
1 in 6 boys and 1 in 4 girls are sexually assaulted some time before the age of 18.  These figures may be low, due to underreporting. In the U.S., there are 37.4 million boys, and 36.0 million girls, all under 18. That’s 6.2 million boys, and 9.0 million girls, abused, for a total of 15.2 million victims of abuse. [This is a population-based statistic, by the way, not a snapshot. Of the population which is now under 18, how many have, are, or will suffer from child sexual abuse: about 15 million.]
How many abusers cover that many victims? If each abuser has one victim, then that’s 15 million abusers. If each has 15 victims, then it’s one million abusers. (Both those figures are too far in each direction, by the way.) From my work with abused children, I would estimate that the typical abuser has several victims. Sometimes an abuser has only one victim, and other times many victims. More typically, the abuser has several victims. The number is limited by the number of children he can access in this manner, secretly. At about 5 victims per abuser, we would have 3 million sex offenders in the U.S.
Then there is the overlap. Often, over the course of their life, a victim is abused by more than one offender. This factor brings the number of offenders higher (because each offender has fewer unique victims). We could have 5 million sex offenders in the U.S., at 3 unique victims per abuser. Depending on the extent of overlap, the number could be even higher.
Now the typical abuser is an adult male. There are about 84 million men, aged 20 to 60 in the U.S. So what would the percentages be? 
5/84 = 6.0%
4/84 = 4.8%
3/84 = 3.6%
Does 3.6 to 6.0% seem too high? Not to me. Think about the different adult men you have known as co-workers, fellow students, acquaintances, etc. Consider the attitudes toward sex that people express online, when they are under cover of anonymity. Would you say that 1 in 20 (5%) has sexual morals of a type that would allow them to sexually abuse a minor, without a pang of conscience? That sounds about right to me.
Edited to add this paragraph: In my more recent post, I discuss an interview that Catholic Baltimore did with Dr. Thomas G. Plante. He states that the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-V) estimates about 5% of men can be expected to abuse children. So these numbers above are about right.
The results of one particular Commission, investigating the abuse crisis in Australia, found that 7% of priests were credibly accused of abuse.  I doubt that figure applies worldwide to priests. But it does support the idea that perhaps as many as 5 to 6% of adult men commit sexual abuse of a minor at some point in time.
In a parish with a thousand adult members attending weekend Masses, I would estimate about 400 are men (40%).  If 1 to 5% of the men are child sex offenders, that’s anywhere from 4 to 20 child abusers sitting in the pews. Some of these men are taking Communion, just as the priests who abuse children take Communion.
The reason that there are priests who abuse children is that there are lay persons who abuse children. Priests come from the laity. The Church’s approach to child abuse does not take account of this fact. The Church’s approach to child abuse does not even address the sexual abuse of children committed by lay persons outside of church property, roles, and activities.
And it is the Church’s responsibility to address this part of the CSA crisis. First, the Church is Mother to all the suffering children of the world. Also, if the abusers and/or the victims are Catholic, it is the responsibility of the Church, all the more.
Second, the Church has the role to teach morality to the faithful and also to the world. CSA is a grave violation of the moral law. Laypersons and priests are abusers partly because the Church has failed to inculcate Her moral teachings into the beliefs and behavior of those She has a right and duty to teach.
Third, the only reliable way to stop the CSA crisis in the priesthood is to address it at its roots: (1) the laity who abuse children, and (2) the laity who, even if they have not abused anyone yet, will abuse when they become priests because they are not in the state of grace and are not living the moral teachings of the Church. As long as there are abusers in the pews, there will be abusers in the clergy.
There is no reliable way to screen out future sex offenders from the priesthood. (Most priests who abuse boys are not gay men. They are abusers who treat victims like objects, and objects do not have a gender.)
Instead, the Church must focus on teaching morality to the faithful in such a manner that Her members live that morality. We can all lookup various moral teachings in the CCC or online. But everyone already knows that the sexual abuse of children is gravely immoral. The Church’s failure is that Her members often do not live the teachings they know.
It’s all connected. Most married Catholics use contraception. That fact proves that the faithful are not living the moral teachings of the Church. So when men apply to the priesthood, the problem is that many of them are not living the moral teachings of the Church. When you have priests who don’t believe, or at least don’t live, those moral teachings, you have priests who can possibly turn into child abusers. Nothing is stopping them. They know the teachings of the Church, but, like most Catholics, they have long become accustomed to violating that teaching without remorse.
Heresy has become a joke in the Church. If a priest or lay leader is accused of teaching heresy, nothing is done about it. Openly contradicting Church teaching is socially acceptable in Catholic society. A popular Catholic priest, theologian, author, or speaker can publicly teach heresy or promote schism, with no negative repercussions from the Catholic faithful. They not lose readers or supporters. They do not lose their job, nor any position in the Church.
The faithful then quickly learn, from their leaders, that they may be comfortable living in contradiction to Church teaching on faith and morals. And this then creates an environment in which a priest can abuse children, then preach a sermon on the Bible and receive Communion, without his conscience bothering him. It is not the custom for Catholics to actually live according to Church teaching on morality, not even when the teaching condemns an act as gravely immoral.
Until the Church succeeds in removing all teachers of grave error on faith or morals, She will not succeed in convincing the faithful to live the teachings. Until the Church prohibits from Communion and other Sacraments, Catholics who do not live the faith, Her members will continue to commit grave sins without repentance. This is the solution to the CSA crisis in the Church: remove all false teachers and require anyone who wishes to attend Mass, receive Communion, or participate in parish life to belief and practice what the Church teaches. Once that happens, you will have driven away the type of candidate to the priesthood who can feel comfortable living in contradiction to the Church’s moral teachings by abusing children.
 “Child Sexual Abuse: What Parents Should Know,” American Psychological Association. (http://www.apa.org/pi/families/resources/child-sexual-abuse.aspx) (February 19, 2014)
 “7 Percent Of All Catholic Priests Were Alleged Sex Abuse Perpetrators: Royal Commission” (6/2/2017)
 Church Attendance Gender Gap Shrinks, But It’s Not All Good News (2017)
 All these population figures are from census.gov, Table 1. Population by Age and Sex: 2015.