The Halakhah of Whisper Networks

In the wake of the #metoo movement, some women turned toward the creation of Whisper Networks for empowerment and protection from future harassment and abuse. Whisper Networks are a network of people passing information from one to another about powerful people who are alleged to be sexual harassers and abusers. Are these Whisper Networks a legitimate way of warning and protecting future victims from abuse? Are they a form of lashon hara, or evil speech, as they have the potential to spread unsubstantiated rumors and tarnish someone’s name? Do they shame the alleged transgressors in a way that violates halakhah and if so, are there instances in which it’s okay to shame someone?