Futures markets and volatility

As Russ Roberts says,

blaming speculators for high prices has always seemed to me like blaming the thermometer for how hot it is

The blogosphere is buzzing about the Onion Futures Act, which - in 1958 - banned the trading of futures contracts on onions to reduce volatility. I've been waiting for someone to post a simple graphic showing a before and after, and Tim Harford has complied:

Of course this doesn't prove anything, that isn't the point. What it shows is that "volatility" is something deeper and more nuanced than merely an unfortunate side-effect of financial speculation. Curiously, I almost wrote "risk management" instead of "financial speculation". Do the terms mean different things? Would the public debate be better informed if we adopted the former?