Whether the bishops knew whether the abusers could be reformed or not, is not the issue.  The abusers committed criminal acts as well as sins -- as well as violations of their vows -- and the hierarchs chose to hide criminals -- criminals who had and were continuing to prey on the most vulnerable members of their Church.  Criminals.  Rapists.  Mental, physical, sexual, emotional abusers.  By all means, try to help them, and forgiveness is available.  But don't hide them in violation of all the laws of God and man. 

Any hierarch who ignored the crime and hid the criminal, claiming he didn't know the criminal had committed a crime or that he might re-offend, was lying to himself and to us, and lacked a well-formed conscience.