Facebook still has a pedo problem because they still haven't hired 1 million employees to deal with it. Amazon would still have a logistics problem if they hadn't hired 1 million employees to move boxes around.
That doesn't support the conclusion that facebook could, stop beating your dead horse.
The idea that this is literally an unsolvable problem is just absurd. If every Amazon warehouse worker instead became a Facebook pedo monitor making a >95% decrease happen would be pretty trivial.