Those who don't have enough of an understanding of how commodity markets work, may be fearful and try to stop the trading of commodities. Unfortunately, most of the labor force and even the educated work force, are incapable of noticing and therefore profiting from price trends so the majority may ask for a ban in commodity trading without really understanding commodity trading.
Trading wheat futures was stopped a few years ago because the futures market was blamed for rising prices. Wheat prices rose quite a bit this year too and margin requirements were raised, on the 6th, to 10 percent. I think that it was unnecessary to raise margins since the price of wheat was going to fall this week and the timing of the margin increases made it seem that it was the reason that the price of wheat has fallen.
Imho, prices can dramatically rise and fall without speculators and I think that speculators are unable to manipulate the markets.
Futures trading is a specialized market and as stated in a previous post on this thread, is
need for hedging purposes (and a healthy economy.)