Listener: Their two witness rule is really a two eyewitnesses rule in most cases
I have thought about this one further and it is obvious that they do accept other type of proofs as well. For instance, if a single sister becomes pregnant, they won't accept "It was the holy ghost." She will be disfellowshiped. Or a brother sent to jail for steeling, even if he claims his innocence, he will likely be disfellowshipped.
So the problem really is the fact that the JW do not encourage the victims to seek out help from the police in order to get the second witness, hence, generally, they are unable to find such witness on their own as they are not police.