Freedom of speech is our most precious freedom of all, because all the other freedoms depend on it. The decision to stop people from exercising this fundamental right must never be taken lightly. Neither should a decision to ban people from visiting this country. As a result, I have in the past defended people with some particularly odious views, such as the recent case of the Australian Holocaust denier Dr Frederick Toben.
In a civilised society, however, there has to be a dividing line between the right to freedom of speech and when it topples over into incitement to hatred and violence. In my opinion, Geert Wilders' revolting film Fitna crosses this line, as its shocking images of violence and emotional appeals to anti-Islamic feeling risk causing serious harm to others.
The key liberal principle was enunciated by John Stuart Mill in his essay "On Liberty", in which he stated that the only legitimate reason for coercing someone against their will was to prevent harm to others. It is precisely the prevention of harm to minorities that justifies the restrictions to Mr Wilders' freedom of speech.
Chris Huhne is the Liberal Democrat home affairs spokesman