So how exactly is this different from $32 to $2 in 2011?
If we're subject to "manipulation" now, we most certainly were manipulated back then.
Non sequitur. Every cod is fish, but not every fish is cod.

Anyway, there must be a way to tell "honest" sells from manipulation. Maybe the one suggested by Richy_T?
We should be able to tell if the dumps are being made at times of maximum or minimum slippage. If minimum, it's someone just selling, if maximum, it's someone trying to get the maximum down-movement for minimum cost.