Some years ago, when I was rather reluctantly having the principles of criminology drilled into me, one of the concepts that interested me most was what was called a symbolic crusade with moral entrepreneurs.

It comes about when a group of reformers seizes upon a topic and uses it for its own purposes.

A good example is prohibition in the US. The Factory Act 1833 is often cited as such a case and, since then, there have been plenty of other such crusades in Britain. For example, there was never any need for the Incest Act 1908. All that was needed was a slight amendment to the Criminal Law Amendment Act 1885, but moral entrepreneurs – such as the Snowdrop Bands and the National Vigilance Association – claimed that, since parental consent (which in practice meant the father) was required for the examination of a child, the act was not working properly.

They used this as an excuse to promote their own brand of morality. All that was really needed was the removal of the requirement of parental consent.

Similarly, the Dunblane massacre was used to get rid of firearms, when what was really needed was a tightening of the regulations before a gun permit was issued.

There is also an argument that the anti-hunting legislation was about class warfare rather than cruelty to foxes. After all, do fish really like struggling against hooks in their mouths, only to be thrown back in the water for it to happen time and again?

And there is at least an argument that the Human Rights Act and the Stephen Lawrence inquiry were good examples of what follows a symbolic crusade.

It is interesting what a head of steam can be generated by a good crusade, and now it seems we are in the midst of another.

This time, the text is the evil of phone hacking, but the sub-text might be seen as the destruction of the power of the press and, particularly, of Rupert Murdoch (pictured) and his empire. There again, another sub-text may be the suppression of investigative journalism. Some members of parliament, for example, are still smarting from the work of the Daily Telegraph last year.

The danger of a symbolic crusade is that everyone gets carried away in a fit of righteousness and more harm than good comes of it. See prohibition (above).

James Morton is a writer and former criminal defence solicitor