The air strikes on Libya are, under the terms of the UN resolution, supposedly intended to protect civilians and result in a negotiated settlement between Colonel Gaddafi and the rebels. This has resulted in some controversy, as air strikes devastated Gaddafi's compound – Bab El-Azizia, the presidential palace abutting military barracks in Tripoli. The defence secretary Liam Fox has insisted, against British army opposition, that Gaddafi would be a legitimate target of air strikes. Assassination, whatever else may be said about it, would leave Gaddafi unavailable for negotiations. But a "compound" – what could be wrong with bombing such a facility?

In situations like this, the usual affective repertoire is unleashed. Gaddafi is a "Mad Dog", the Sun, the Mirror, the Star and the Daily Record inform us – an epithet first applied by Ronald Reagan when the latter bombed Gaddafi's compound, among other targets, in 1986. He is "barking mad", they say. Jon Henley in the Guardian went further – not just "barking mad", but "foaming at the mouth". "Cowardly Colonel Gaddafi," the Sun almost alliterated.

I grant that Gaddafi is a dictator whose determination to hold on initially seemed to defy reality. Yet the reality is that he has shown every sign of being a canny operator, from his rapprochement with the EU and US to his outmanoeuvring of the rebels. Besides, such language has connotations which overflow its formal significations, and does important ideological work in the context of war. It might help to look at an example of this at work.

The Sun, having suitably vilified Gaddafi, informed us that he had "ordered his armed forces to dress in civilian clothes in a bid to trick Our Boys into aborting their bombing runs". At the same time, he "had around 300 'supporters', including children as young as five, in the grounds of the compound in the Libyan capital at the time – all unaware they were acting as his human shield". By means of such prophylaxis, the Sun sought to assure readers that if anyone was killed, they weren't civilians. And if they were civilians, it was because Gaddafi had engaged in a dastardly ploy to use civilians as a human shield. Either way, "Our Boys" are pre-emptively cleansed of any of the bloodshed, though it is they who are the bombers in this instance.

The demonology is intended to make such ridiculously convoluted tales more plausible. And it has a long history in the annals of British war propaganda. At the height of the Suez debacle, the BBC described Gamal Abdel Nasser as a "barking dictator". Saddam Hussein was also a "mad dog", "barking mad", "foaming at the mouth", "Hitler" and more besides. And he too was blamed not only for the nonexistent WMD but for situating his military targets among civilians, thus using them as human shields – as if the British government routinely situates administrative buildings and MoD offices in the middle of deserted fields in Berkshire. The effect of such rhetoric is to externalise evil. The same states that brought us Fallujah, Guantanamo and Abu Ghraib can, through such means, claim a monopoly on the moral high ground.