I worry about Gerard Henderson, really. He has a chronic case of corresponditis — the inability, at the end of a protracted exchange of letters, to allow his correspondent to have the last word.  Whenever clinicians consider this affliction they go straight to the Sydney Institute’s Media Watch Dog website. It is a case study in fanaticism, always a worrying state-of-mind in public life.

It is said that the definition of a fanatic is someone who redoubles his efforts when all is lost. This captures the Henderson method.  Even when he is hopelessly wrong, he keeps churning out correspondence.  Write a letter raising the slightest hint of criticism and he will send you a post office-full of replies. Al Gore might have invented the internet but by sheer weight of emails, Gerard is close to busting it.

I first encountered Gerard and his wife, Anne, at the launch of Barry Cohen’s compendium of quotes Whitlam to Winston in 1997. At the peak of their form, Gough Whitlam and Tim Fischer gave witty speeches, complementing the amusing anecdotes in Cohen’s book.

The only sour note came from the rear of the room, as Anne Henderson heckled Whitlam, complaining to her husband, “Why do we have to stay and listen to this man?” Onlookers were left wondering why she attended at all, given that “this man” was listed on our invitations as the book-launcher. Perhaps she thought she deserved the last word, even at someone else’s function. Discreetly, Gerard led her away … back to the Institute where, in the finest traditions of Sydney-town nepotism, Anne was (and remains) the deputy director.

By now, I can feel a letter coming on. So I might as well make it a long one. Gerard is the everywhere man of Australian pedantry. His life’s work is to find faults in others, but herein lies the Henderson paradox. For someone who delights in pinpointing errors, he is notoriously sensitive to criticism. Stories of his volcanic over-reactions when confronted with his foibles are legend in Australian politics. The kitchen is too hot for Gerard but there he sits, day after day, compiling his latest letter-bag.

More than any person I know of, the adage applies: who will guard the guardians? What right does Henderson have to launch a campaign against the accuracy of Malcolm Fraser’s memoirs (as he did recently) when his own work is riddled with errors? Who gave him a roving commission to censor prominent Australians on major issues such as climate change? There is an underlying conceit to Henderson’s approach, a persistent attempt to elevate himself above others. He is what is known colloquially as a “know-all”.

He certainly knows how to make errors. For every mistake he identifies in the work of his political targets, he makes one himself — the mother of all hypocrisy. His standing in Australian public life is unique, as a clumsy pedant. This shortcoming runs deep, with scores of stuff-ups pinned to Henderson’s file. Let me list a small proportion of them.

Gerard has a particular problem with Australian political leaders. In The Sydney Morning Herald in June 2008 he declared that during the Iraq War in 2003, the leader of the Labor opposition was Kim Beazley — it was, of course, Simon Crean. His Sydney Institute website lists Barry O’Farrell as a Member of the Legislative Council, a chamber from which, constitutionally the NSW Premier could not lead his government. Last year Henderson described O’Farrell’s predecessor as “the sassy Christina Keneally”. Her real name is Kristina.

When a similar mistake was made in Fraser’s book, Henderson thundered, “This is not a typographical error. Rather it is a significant howler.” By this standard, Gerard is running a howler-thon. Self-awareness is not his strong suit.

This is the sad side of corresponditis. Having tried to carve a career from monitoring other people’s mistakes, Henderson is one of the Herald’s most error-prone columnists. A big statement, I know, but I have seen the sad side first-hand. In March 2006 he claimed that the entry in the Latham Diaries for January 9, 2002 was not genuine. As readers of my book will know, I did not make a diary entry for January 9, 2002.

In 2009 Henderson wrote that Foreign Minister Stephen Smith’s meeting with the Chinese minister Zhou Yongkang was held in secret. It was not. In November 2009 he confused Nick Minchin for George Brandis, an embarrassment for someone who regards himself as Australia’s leading authority on the Liberal Party. In July 2010 he referred to a Per Capita board member Josh Burnside (it was, in fact, Josh Bornstein). Henderson also consistently confuses “electors” (people on the electoral roll) with “formal voters” (electors who cast a formal vote) — a damning ignorance of Australia’s electoral laws.

Recently, doubts have even emerged about the authenticity of his work. The Sydney Institute website reprints his Herald columns under the banner “Gerard Henderson’s Weekly Column”.  When I looked at the site on Tuesday morning, the entry for May 17, 2011, “Middle-class welfare tag insults the noble art of raising children”, was listed as having been written “by Viren” – that is, Viren Nathoo, who works for the institute. If Henderson’s Herald columns are being ghost-written by Nathoo then surely the paper’s readers should be advised accordingly.

Adding to the confusion, 11 so-called “Gerard Henderson” columns at the end of 2010 and beginning of 2011 are given the authorship “The Sydney Institute”, again suggesting the involvement of Nathoo. Either ghost-writing has been undertaken or, in the accreditation of the columns, another significant howler has been committed. Either way, Henderson’s credibility is diminished. If he cannot run his own organisation efficiently, how can he be trusted as a political and cultural commentator?

The other inconsistency in Henderson’s work is ideological. As a conservative he should respect freedom of expression in civil society. On June 2, on Sky News’ The Nation, however, he argued that Cate Blanchett, Tim Flannery and Tim Costello should not publicly support the introduction of a carbon tax because they use carbon-reliant aeroplanes. As an extension of this logic, it would be hypocritical for someone living comfortably on Sydney’s lower north shore, rubbing shoulders with Australia’s business and political elites in a corporate-subsidised job, to have spent the past 25 years advocating labour market deregulation and lower wages for Australia’s working poor. But that’s Gerard Henderson (aka Viren Nathoo) for you.

He took a similar stance concerning my involvement in last year’s federal election, writing on August 10 that “the former Labor MP for Werriwa is doing quite well (financially), per courtesy of the Australian taxpayer, and does not need to work for Channel 9’s 60 Minutes program during the election campaign”. This is a throwback to socialist economic control, when individuals do not have the right to determine their own employment and income levels.

Henderson and Nathoo know nothing of my household expenses and financial commitments. Their knowledge of my income is limited to publicly disclosed superannuation ($78,000 per annum). Yet in an astounding display of arrogance, they presume to tell me, my wife and our three dependent children that we are “doing well” and do not require other sources of income. In practice, Henderson is not against centralised income planning, as long as he is the central planner. His commitment to labour market deregulation is purely rhetorical.

I have consulted experts across the globe about this affliction. They say there is only one remedy for corresponditis. Henderson needs to write less. Brevity will deliver greater accuracy and less hypocrisy in his work. So Gerard, old chum, put away your stamps and envelopes, your letter-file is full.