While Apple understandably may be very reluctant to disclose review validation / fraud detection methods, they could certainly show some trusted media figure -- Marco, some other popular ios developer, maybe even Gruber -- some detailed bit of proof and put this controversy to rest. If, indeed, they have any proof.

That would be pointless because these people would be accused of being shills who would always sing praises of Apple. There's no easy way to handle giving away the proof and having an expectation that it would indeed help Apple. Depending on the material, there could be nuances that could be interpreted out of context…the context being the entire chain of events and internal and external communications that took place.