First amendment doesn't forbid the government from making filing a false criminal complaint a crime. Sure there's the court of public opinion, and civil court remedies, but I was talking about false reporting to police and prosecutors, etc official government agencies and processes as far as what they should be doing more about. The acts of libel that don't amount to the same criminal charges, can still be used as evidence to convict. And the accusations of crime so vile should be reported to police, not just an online audience. If the audience is important enough to report the allegations of abuse to, then they should be interested in the possibility that the accusations are false, and demand justice.