It is not the initial crime that is so shocking. Every religion will attract pedophiles, particularly those with access to children without much scrutiny. As with Watergate and the Roman Catholic Church, it is the cover up that is so bad. I see no scriptural basis for the two witness rule. How many pedophiles will do it in front of an adult? They confuse legal standards with Christian standards. Allegations alone should not be enough to condemn someone. Look at how many Sandusky victims have stepped forward since the publicity.
The criminal law does not require two witnesses. There are other probative criteria to employ. Lie detector tests, consistency with other children's stories.
I don't know anything about the pedophile underground but the Witnesses provide unsupervised access to children, children with pathological deference to adults, many boys without fathers (if my KH was normal).