They're the agency that is investigating and charging people with the crime-they're not supposed to be neutral. It's the judge and jury that are supposed to be neutral at trial.
They are too biased these days though. The FBI selectively persecutes, so the reason this is frowned upon is because of the latent corruption already in the system.
I'm not sure how that claim has anything to do with this situation. Are you saying the FBI is somehow persecuting BreachForums because of corruption? That doesn't seem very likely to me. It seems much more likely that the FBI are trying to prosecute the people behind BreachForums because it is a marketplace for illicit activity (eg exploits, ransoms etc). The intent is pretty clear is in the name of the forum really.
