Eg, they plant a hidden camera in your house, see you packing drugs and puting them in your car in your own garage, and driving away. Since they got the info that you had the drugs from illegally set cameras, they can't just stop and search your car, but they can "randomly" stop you for a traffic check, and just "randomly" have a drug sniffing dog present, which finds the drugs in your car.
If the judges let this go through, the police would use more illegal methods (illegal searches, etc.) to gather data, then just "randomly" detect crime, and then the state would win cases.... and we (the people) don't want that. That's why, if you prove, that they knew the drugs were there from an illegal source of information, everything derived from that illegal source should be dropped as a illegally obtained evidence, to disincentivise the use of illegal methods.
Basically, the officer saying they randomly stopped you, would be a lie (=perjury), because they stopped you due their illegal cameras.