That being said, Zille has made a number of errors of late. The most recent is her publication of a statement entitled "Mandela's leadership long forgotten in Aids debate" in the DA forums. There are a number of serious problems with the statement, but I shall focus on just two: Zille's misuse of metaphor, and her misunderstanding of the role of race in debates about HIV infection in South Africa.

In the statement, Zille rails against a group of people "who actually have much in common with religious fanatics or fascists . They hunt in a vicious pack to prevent anyone from questioning their assumptions. Slacktivists is too gentle a word to describe them. They are more like an Aids gestapo."

Who are these wolfish folk, one wonders. Are they the ranks of Treatment Action Campaign activists who marched to courts and clinics demanding public access to life-saving antiretroviral treatment? Are they the activists who occupied the South African stand at the Aids conference in 2006 to draw international attention to the travesty of the government's obstruction of treatment?

Or are they the leaders of the HIV treatment-access movement? With this last possibility, I pictured the leaders of TAC and the Aids Law Project prowling the picket lines, wearing vampire teeth, and charging the gates of parliament.

Sadly, Zille doesn't fulminate on the ranks of the "Aids gestapo", but names only one alleged henchman, clinician and researcher Dr Francois Venter, one of the leaders of the HIV Clinicians Society of Southern Africa.

For some time, Venter has been engaged in a debate among public health specialists about the reasons for the high prevalence of HIV in South Africa. As Zille mentions, he has posited the possibility that there may be a genetic or environmental factor that makes South Africans more susceptible to HIV infection.

He writes that "there is accumulating evidence that people in our region are more vulnerable to HIV per sex act than our European, Asian or American counterparts".

Calling this argument "the ultimate cop-out", Zille accuses Venter of "enforcing denialism".

If Venter has time - between his work at the Reproductive Health Research Unit, editing a journal for HIV clinicians, and treating people with HIV at a public clinic - to register this accusation, I'm sure he'll be amazed.

It is a scientific fact that certain groups have a greater genetic predisposition to some diseases. To say that Jews are more likely to develop Tay-Sachs disease is not anti-Semitic. By the same token, Venter's suggestion that there may be a genetic or environmental predisposition to HIV for people in South Africa is not to demonise one group, nor to negate anyone's responsibility for safe sex and behaviour change.

Rather, it is to pose a scientific hypothesis for the high rates of HIV prevalence in South Africa, and to call for further research to determine the veracity or falsity of this.

This brings me to Zille's misuse of metaphor in the article: her use of the phrase "Aids gestapo".

As with slavery, the Holocaust occupies a specific place in the public imagination, symbolic of oppression and brutality. The iconography of the Holocaust, such as the yellow Star of David - which Jews were made to wear on their concentration camp uniforms - is etched into our collective consciousness, as are terms like "gas chamber", "swastika" and "Gestapo". Because of both the significance and ubiquity of Holocaust imagery and rhetoric, they have been misappropriated to mobilise support for causes, as in the description by anti-choice activists of abortion as "America's holocaust".

There may well be instances in which comparison between appalling events in history is justified. I am not arguing that the Holocaust was the "worst" event in history, or that the suffering of the Jews was greater than, say, the victims of the genocides orchestrated by Stalin, Pol Pot and Nahimana.

But I am arguing for caution and discernment in the application of historical terms, the meanings of which derive from specific events or processes. If we misuse terms that arise from historical instances that stand for grievous injustice, we cheapen their meaning, deaden public response and disrespect the memories of the victims. Zille's use of the term "gestapo" is such a misapplication.

Her comparison promotes a lack of understanding about the true role of Hitler's Gestapo, the extraordinary injustice of its activities and the suffering of its victims.

Instead of adding weight to her argument, Zille's misuse of metaphor renders it valueless.

What is more, she slides into the realm of conspiracy theory when she poses the question: "Did the Aids gestapo silence Mandela?"

Casting aspersions on scientists, mining history for lurid comparisons, and trumping up charges against Aids activists? Doesn't Zille realise she sounds just like former president Thabo Mbeki?

• Hodes is deputy director of the Aids and Society Research Unit at UCT. This is an edited version of an article that first appeared on www.dailymaverick.co.za