FBI can manufacture probable cause at will on an anon board. Just post incendiary material. I believe the posts here that advocate violence are by FBI.
Notice the FBI is skilled wordsmith. Comey told Trump he (Trump) wasn;t under investigation, but others in the FBI viewed that as a lie, because Comey knew investigating the campaign inevitably involves investigating Trump. Comey justified the lie.
Same for monitoring websites. FBI says it only does that with probable cause. It says that to fool the public. It is technically true, but the FBI manufactures probable cause wherever it has curiosity or animus.