Paranoid bullshit, easily disproved by the fact of people serving very long prison sentences based on an abundance of evidence. These cases are generally not that hard to prosecute because offenders typically have a wildly distorted risk calculus and either incriminate themselves to someone they imagine shares their tastes, or because search warrants turn up a ton of physical evidence - sometimes quite literally: https://cbs12.com/news/local/child-pornography-arrest-paul-z...