I've seen a documentary last week talking about this.
Pastors were not allowed to marry, because if they found a family, when the pastor dies, all his money will go to the family. But if he's alone, the money will go to the church.
This caused several problems. Since they are not allowed to be with someone, they do not have sex. People were confessing about sexual "sins" a lot. The pastors were to listen to their stories. That was their "porn" because they weren't allowed of anything else.