LOL That would only be true if they were willing to break the law (by blackmailing somebody, yet felt the strange need to making a
legal accusation.
It's very hard to defend against institutional blackmail. The blackmailer just has to make their demands, that need to be followed "if you known what's good for you". Generally, that will work and no further steps are necessary.
If somebody decides to resist the demand in any way, you simply place some of those pictures of underage kid - perhaps from the project mentioned in this article - and place a "tip" with the local police. Of course, they could always "parallel construction" it. Many options there, because you never actually have to show real evidence in court, or even show up. You just have to get the ball rolling, and the child-porn accusation will do the rest for you.
In fact, it's important to make a big show about it, because coming down hard on the occasional person that questions your demands serves as an excellent way to discourage other from trying.