There is no rational argument behind this. "Liberal" is supposed to be a word that gives people warm, fuzzy feelings, and "illiberal" some sort of deviation.

Criticising long-term supply contracts by non-UK agents as "illiberal" is a way of protesting for not having had the foresight of entering into said contracts years ago. Denouncing these contracts is actually a statement that the freedom of contract and the enforceability of contracts are only good when the contracts involve The Right People™ (London or NY capitalists, basically).

Now, as yuo hint in your comment, the volatility of price (but also supply levels) in commodities markets (or any markets) actually hurts the companies that depend on those markets, who would rather have predictable prices and dependable supply (and demand) levels. And so, those who can do enter into long-term supply contracts. Other ways to escape market volatility include vertical integration where you just buy a supplier outright.

All this was said better by the elder Galbraith in The New Industrial State. The "liberal" "free market" economy is a myth which does not describe the workings of the industrial economy. All large successful corporations escape "the market" and its uncertainties and mechanisms such as antitrust laws or incantation about "liberal" economics and "the free market" are more designed for reassuring the public or for justifying that which is actually done for expediency reasons.

The peak-to-trough part of the business cycle is an outlier. Carnot would have died laughing.

JakeS:

Do economists seriously postulate that there is a difference between buying a future from GazProm and buying a future from GoldmanSachs?

The OTC (Over-the-counter, off-exchange) market is good if your counterparty is Wall Street, and it is bad if they are brown or speak funny. [PN: you trade futures in an exchange, but enter into forwards bilaterally off any exchange]

JakeS:

I mean, I can see why it would bother the City of London that the supplier and consumer hedge risk bilaterally rather than through a middleman. But surely it shouldn't matter to any sensible model of risk management?

From the point of view of risk management you could have a bilateral agreement (both parties carry the counterparty risk), or an agreement through a middleman (the middleman takes the counterparty risk, assuming the middleman is less likely to default that either counterparty), or a transaction though an exchange/clearing house (the clearing house takes the counterparty risk, and the risk is mitigated though margin accounts).

JakeS:

Do economists seriously postulate...

I don't know about "economists", but "The Economist" clearly seems to.

But not really if pressed, I wouldn't think. The point of The Economist's piece is not rational argument about hedging but narrative-pushing about the UK's position in the energy markets.

The peak-to-trough part of the business cycle is an outlier. Carnot would have died laughing.

JakeS:

Why does hedging risk not fit with the accepted fairytales about the market?

The acceptable fairytales say that hedging is done by trading derivatives (preferably cash-settled!) in an exchange. Entering into a long-term contract is an old-fashioned, borderline socialistic, monopolistic practise. Get with the times, Jake!

The peak-to-trough part of the business cycle is an outlier. Carnot would have died laughing.

Do economists seriously postulate that there is a difference between buying a future from GazProm and buying a future from GoldmanSachs?

Selling futures is a seriously profitable activity. So yes, there is a BIG difference: in one case, the profits go to Gazprom, and in the other to Goldman Sachs. surely you can see how how outcome is much preferable to the other one (if you are Goldman Sachs or one of their sycophants)...

In the long run, we're all dead. John Maynard Keynes