You shall know democratic politicians by their fruits, to rephrase Matthew 7:15-20 somewhat.

When he was communications minister in Tony Abbott’s government, Malcolm Turnbull was relaxed about the ABC. His view was, since most journalists were on the left, it was to be expected the ABC would promote left-wing causes that reflected the political and social views of its staff. Hence Turnbull’s reluctance to endorse Abbott’s criticism of the lack of balance at the public broadcaster.

Unlike Abbott, the Prime Minister is not much interested in cultural issues. But he does care about economics and business. That’s why, in the House of Representatives on February 14, Turnbull delivered one of the most scathing attacks on the ABC in recent times. At issue were two articles on the ABC website by chief economics correspondent Emma Alberici.

The first was titled “There’s no case for a corporate tax cut when one in five of Australia’s top companies don’t pay it”. This was taken down on February 16 and restored in a revised and updated form last Tuesday.

A second piece by Alberici, “Tax-free billions: Australia’s largest companies haven’t paid corporate tax in three years”, was updated by the ABC “to provide further information and context”.

On February 16, the ABC issued a statement that Alberici’s first article did not accord with its “editorial standards for analysis”. Paul Barry, on ABC TV’S Media Watch program last Monday, said ABC news director Gaven Morris expressed concern with Alberici’s article within a couple of hours of it being published. There is no reason to doubt this.

Clearly Turnbull’s bucketing of Alberici’s analysis came after the ABC had set in place its own review procedures. But Turnbull’s evident anger in question time on February 14 demonstrates that his past tolerance for a lack of balance at the public broadcaster does not extend to matters such as the rate of company tax.

The essential problem with Alberici’s view was that she appeared to confuse a company’s profits with its revenue. Company tax is levied on the former, not the latter. This confusion became evident when, on ABC Radio National’s Breakfast program, Matt Bevan declared that Qantas had not paid tax on a $110 billion profit. He should have said revenue, and presenter Fran Kelly soon had to issue an apology.

In the event, Turnbull, Scott Morrison and Communications Minister Mitch Fifield all took up the matter with ABC managing director Michelle Guthrie. This led to a rare but appropriate backdown by the public broadcaster, which is not known to admit readily to errors or make corrections.

In a sense, it’s easy to feel some sympathy for Alberici and Guthrie on this issue. It seems to have been during Mark Scott’s time as ABC managing director and editor-in-chief (from 2006 to 2016) that the distinction between analysis and opinion was breached irretrievably. This coincided with the advent of social media.

During Scott’s time, ABC presenters were encouraged to become personalities on Twitter, podcasts and the like. They were urged to take part in panel discussions where they were expected to opine on, well, almost everything.

When Scottish BBC presenter Andrew Neil spoke at the Sydney Institute in April 2014, he declined to state a view as to whether Scotland should remain within the United Kingdom. The referendum on Scottish independence was then a live issue. I feel Neil wanted Britain to stay intact, but he did not say so. In fact, Neil commented that BBC presenters were not allowed to express personal opinions on controversial issues.

The ABC’s current editorial policies declare that “even specialists should stop short of prescriptive conclusions or over advocacy of one position over another”.

Yet the likes of Alberici, Kelly, Philip Adams, Julia Baird, Jonathan Green, Leigh Sales, Virginia Trioli and others regularly make contributions on traditional and social media where they do precisely this — with the encouragement of ABC management.

The matter is complicated by the fact the public broadcaster remains a conservative-free zone. The ABC does not have one conservative presenter, producer or editor for any of its prominent television, radio or online outlets. Not one. This means contributions to the public debate from ABC presenters invariably come from the left-of-centre or green-left perspective.

In the lead-up to the same-sex marriage postal survey, ABC management felt the need to remind staff that 40 per cent of Australians believe marriage should be between a man and a woman. It was good, and as it turned out accurate, advice. But it’s difficult to think of anyone at the public broadcaster who would line up with the minority position.

The lack of any conservatives in prominent positions at the ABC leads to a situation where the public broadcaster seems to speak with one voice on issues such as same-sex marriage, climate change, border security and more besides. In recent years, even comedy on the ABC has become partisan. Writing in The Drum on March 11, 2016, Michael Jensen (rector of St Mark’s Anglican Church in Sydney’s Darling Point) commented that Australian comedians had “turned into preachers, moralisers, and puritanical do-gooders, whose mission in life is not to make us laugh but to tell us what to think”. He named ABC personalities such as Charlie Pickering and Adam Hills.

The tradition continues. On February 15, ABC Tonightly’s Tom Ballard did a 10-minute rant advocating for renewable energy and bagging coal. Anyone with a different position from the one-true-green-left faith was ridiculed.

It was much the same in Shaun Micallef’s Mad as Hell program last Wednesday when there was a rant mocking the Catholic Church concerning the sacrament of confession. Micallef and his team seemed unaware that few Catholics go to confession these days.

The problem with the ABC is that its stars all seem to bang the same drum. This is broadly tolerated by the Turnbull government, except when someone dismisses the need for corporate tax cuts and stumbles in the process.