I haven't watched the vid, but I'll take it as fact that the statement from the above poster is accurately ascribed from it.
Why should anyone think that <i>futures</i> prices should have anything to do with supply and demand? Supply and demand usually meaning <i>current</i> supply and demand.
Speculators are guessing what is going to happen in the future, and it takes into account a lot of other things besides current supply and demand.
So many people have a problem with GS bidding up stuff that's going up and then shorting it at the top. Isn't that what a good trader is supposed to do? The critics think that the big IB's are supposed to buy at the top and sell at the bottom. That's what'll make the critics happy. lol