How does one balance the rights of the vulnerable, who sometimes do need to be anonymous for fear of retribution and the people who use anonymous accusations as a harassment strategy or for political purposes or for a witch hunt?

The only way seems to be to have a more-or-less independent panel who would look at the anonymous accusations and make an impartial decision on the same. The legal system, as it exists, seems to be such a body, definitely much more impartial and unbiased than a random administrator in Stanford.