There's broad protections for reporting crimes incidentally observed. It's why parallel construction exists in the first place - to avoid the absurdity of happening to observe a murder, but then grant immunity to the victim due to how it was initially identified even if you later find the body, weapon, and DNA evidence.

In the case of Tor, when you go probing hidden services it would be very easy to find a lot of crime you'd definitely want to report if you knew who was doing it.