Ken,
I don't know how you can figure he's dumping chips pre-flop. He just might get lucky and win with any holecards...so how can we accuse him of chip dumping? Remember, he's all-in, so he must show his hand.
What does a player's holding (pre-flop) have to do with anything? Maybe he's bluffing. The best players are always telling us that they play the player, not their cards.
IMO, chip dumping is difficult to assume, and virtually impossible to prove, in your scenario.