The arts world is wallowing in a moral mire. Last month, I wrote about explicit images being portrayed in an exhibition at the Hayward Gallery, and the warnings attached to it. Within a few weeks visitors to another gallery had another notice to read: Tate Modern put up a warning about the Richard Prince photograph of a naked 10-year-old Brooke Shields, part of their Pop Life exhibition. Already no one seems to remember exactly what the words were, but the Tate says it read, ‘Something like … “Visitors may find the image in this room challenging in content.”’

But words can’t protect you from the power of an image. Saying it’s going to offend isn’t a defence against it offending. In the “photograph of a photograph”, Shields’ pre-pubescent body is smothered in oil as she stands in a marble bathtub, her hair and face heavily made up. Although the picture had been displayed without comment at the Guggenheim two years earlier, Scotland Yard felt it was their duty to intervene under Britain’s obscenity laws. Officers from the obscene publications unit arrived on the first morning the exhibition was going to be open to the public (30 September) and advised the image be removed. Interestingly, the press had already seen the photograph at an earlier opening without any legal intervention, as had those invited along to the private view the night before. Are arts correspondents and Tate sponsors of sounder moral mind than those who pay to enter an exhibition?

The Tate is very shy about the exact circumstances of the image’s removal from the gallery wall. They won’t even confirm whether the officers arrived with a search warrant. All they’ll say is that the “room is temporarily closed while in discussion with the police”.

What sort of discussions? And shouldn’t these discussions be held in public, not between the authorities and a single museum? Surely the issues raised here – the relevance of context in displaying difficult images, permission from those portrayed, obscenity, censorship - are pertinent to every gallery. It’s disappointing that there has been, as far as I know, very little attempt at any open debate about this removal. Couldn’t the Tate have used its very powerful position within the cultural sector to lead on such a debate, welcoming the opportunity to bring these issues out into the open and get visitor feedback? Instead, it’s working towards a few handshakes and secret agreements behind closed doors.

The other big child abuse story connected to the arts in the last month has been handled very differently. Movie director Roman Polanski has been arrested in Switzerland and is facing extradition to the US on charges of raping a minor in 1977. Here, the arts have come out in support of their own. It’s a shameful stance. Here’s a man who has pleaded guilty to having unlawful sex with a 13-year-old while also, undeniably, making a few very good films. But just as putting up a warning isn’t a defence against displaying obscene images, so making groundbreaking movies isn’t a defence against child rape.

To anyone outside the cultural elite, the case for Polanski’s extradition seems clear cut. The removal of the image at the Tate Modern isn’t so simple. But this instinct behind being vociferous about the film director and ignoring the removal of the photograph is the same – to close ranks. Both being outspoken in support of Polanski and silent over Brooke Shields only makes the public more suspicious of the artistic community, believing it to be small and self-serving.

Only when the creative industries open tricky issues up to public debate will they gain the trust of their visitors and viewers. Sadly, these two events have shown that they’re incapable of doing so. Yet.