FOR the first democratic election 20 years ago, the African National Congress ensured it would not enter the election period without the SABC — for so long a voice of the ruling party — being put into neutral hands. It understood the power of the national broadcaster as the primary source of news and information for most of the country, and its capacity to distort the national debate and influence voting. Now it appears we are entering an election again with the SABC — or at least key elements of it — captive to a ruling party.

One would expect a public broadcaster to bend over backwards to show its neutrality at a time such as this. If there was a potential problem with a party political advert, then you would hope it would convene a special committee to consider it carefully and show clearly why the advert is a problem. It would at least tread cautiously. But the letter the SABC sent last week to the Democratic Alliance (DA) to explain why it pulled the party’s advert off the air gives the opposite impression: that it was scrambling around for ways to protect President Jacob Zuma, searching the rules to find reasons to justify stopping the advert.

The letter gave four reasons for not running it. It said pictures of police shooting protestors "is cause for incitement to action against the police services" and that the Regulations on Political Advertising and the Electoral Code of Conduct prohibit "language which provokes violence". The DA is not accused of using such language, just of showing images that might give cause to some to incite action against the police. This is tortured logic — verbal gymnastics by lawyers trying to justify a political decision after the fact.

It is true that the brief image referred to is shocking, but that is exactly why it needs to be seen. If you are going to stop pictures of police behaving badly, you are going to seriously undermine the media’s capacity to hold authority accountable.

The second reason given is that the rules prohibit false information about other candidates or parties. "We believe this can also be extended to information that has not been tested and confirmed in a court of law." Interesting, isn’t it, that it is reduced to something the SABC believes? Not a legal or ethical principal, just a belief. Also worth noting is that it is not sufficient for the allegations to have gone through a chapter 9 institution. This would rule out all the Nkandla allegations, and about half of our political debate. It is a ludicrous, though familiar, argument, often used by officials to stall action against those accused of misconduct.

The SABC also says that the Advertising Standards Authority (ASA) does not permit advertising attacking another product to promote your own. It acknowledges that the ASA has no jurisdiction over election advertising, but says it believes the broadcasting regulator, the Independent Communications Authority of South Africa, would take the same view. Again, it is asserting an untested belief and giving no details of which elements of the advertising it feels cross the line. The lack of specifics is a telling sign of the weakness of an argument.

Finally, the SABC says it will not permit personal attacks on any political leader. One might ask when a criticism becomes a personal attack, but this reasoning might explain why SABC news has become so boring. If you vaguely circumscribe criticism of political leaders and the capacity of one party to take on another, you are going to have a very dry election debate. You are saying that character and conduct are not election issues.

Pulling party adverts a few weeks before an election is a serious matter. The SABC needs to put in place a more plausible process for ensuring that it is only done in extremis and in a way that puts it beyond question. It is essential that it tests its view in open debate and puts enough meat on the allegations (such as exactly which phrases are unacceptable) before disrupting the elections process.

One surprising element is that SABC editors are silent. This was described as an "editorial decision", though it appears to have been made by the chief operating officer. Where are the editors?

• Harber is Caxton Professor of Journalism at the University of the Witwatersrand.