In 1950, when the Communist Party of Australia was banned by the Menzies government, police raiding militants often compensated for their ignorance of socialism by simply confiscating all books with red covers. The legendary Sydney waterfront activist Stan Moran supposedly even convinced constables that a portrait of Karl Marx merely depicted a jolly old Santa.

The revelation that anti-terror police conducting last month’s much-hyped operation in Sydney seized a sword made of, um, plastic suggests that the traditional incomprehension of Marxism has given way to a new incomprehension of Islam.

As Fairfax’s Rachel Olding points out, the sword taken from the house of Mustafa Dirani featured prominently in the media’s coverage of the alleged beheading plot.

“Was this the lethal sword terror cell planned to use to behead an innocent victim on a Sydney street?” asked the Daily Mail. To which we can now answer: no, not so much.

Almost all the sensationalist claims made immediately after the Sydney raids and the Melbourne shooting turned out not to be true. In both cases, references to “beheading” were a complete fabrication.

But Olding’s piece reveals something even more disturbing. The blade depicted so menacingly in almost all the newspapers was a Zulfiqar, an unremarkable symbol of Shiite Islam, generally purchased from religious shops.

Dirani’s family are Afghan-born Shiite Muslims. Why, then, was Mustafa Dirani being raided in connection with the Islamic State, a Sunni group notorious for massacring as apostates any Shias who fall into its clutches?

As Patrick Cockburn explained earlier this year, “simply to be identified as Shia or a related sect, such as the Alawites, in Sunni rebel-held parts of Iraq and Syria today, has become as dangerous as being a Jew was in Nazi-controlled parts of Europe in 1940”.

The whole business highlights the profound inadequacy of the discussion of Islam in Australia: in particular, the inane division between “radicals” and “moderates”. You only have to apply the schema to Christianity (though of course no one ever does) to recognise its stupidity. Is, say, the Archbishop of Canterbury a “moderate” Christian? One imagines that Justin Welby would claim to practise his faith as fervently as any Pentecostal (albeit with different rituals and customs).

But while conventional opinion accepts the divisions between the followers of Jesus as doctrinal differences that need to be taken seriously, Muslims remain categorised according to temperament: basically, whether they’re wild or tame.

In a press conference after the raids, New South Wales Police Commissioner Andrew Scipione said it was “perplexing” that a tiny minority of young people would “choose death and terror and the values of ISIS over the freedom, choices and lifestyle that is [sic] available to all Australians”.

We know now why Scipione was perplexed — his men had just raided Dirani and his friends on the basis that they supported a group that wanted to kill them.

Did ASIO, an organisation with an annual budget of nearly half a billion dollars, really think that Shiites would belong to an organisation dedicated to massacring Shiites? Or were they simply happy to let the Diranis be swept up in the hysteria that, predictably enough, resulted in extraordinary new powers for ASIO?

It’s hard to know which option is more disturbing.