The people making these comments have either a reading comprehension problem, or no knowledge of history, and probably a little of both. What was being suggested was a government supermarket chain that would compete with the existing businesses, not a commie takeover of them all.
More competition, in other words.
Anyone who wants to continue throwing billions of dollars into the pockets of international shareholders would be absolutely free to do so. And if you don't like the idea of a government-owned chain that would steer people to fat- and sugar-free choices (thereby reducing the country's gargantuan health bill), pay staff and suppliers decently, and champion locally-produced goods, no one would be putting a gun to your feverish head.
When they've stopped clearing the reds out from under the bed and re-reading The Fountainhead, maybe the critics could consider that the way things are going is unsustainable, and that at the very least, governmental forces will need to step in to ensure the duopoly "plays nice".
If that isn't a failure of the current system, what is? There are plenty of other supermarket models around the world we can draw inspiration from, even if going the govt-owned route isn't acceptable. We don't need to go all Abasto Bicentenario (Venezuela's Bicentennial Grocery Stores) on it, but frequently, stronger government does provide an answer.
In China, where there's a more favourable regulatory environment for local players, to India, where some regions expressly forbid foreign grocery chains, to Brazil, where the government runs popular, low-cost restaurants and provides several meals a day to those deemed "in need", many countries acknowledge that extra steps are required when the free market fails.
There are extra-governmental ideas, as well. A few readers steered me to Migros, Switzerland's largest supermarket chain, which is run co-operatively: two million Swiss consumers own the business. The chain's main stores do not sell tobacco, alcohol or porn. Over 90 per cent of its goods are produced by local subsidiary companies.
Too "nanny state" for rugged Kiwi individualists, no doubt, and you'd have to be a Bolshevik to even suggest a mandate to buy locally-made. Meanwhile, Prebble and co are once more wheeled out to promote more of their 1980s solutions.