I wouldn't be beating this issue to death except that I see people such as British MP Chris Huhne attempting to justify the exclusion of Geert Wilders from the UK (and seemingly to advocate censorship of his short film Fitna) on the basis of the harm principle of John Stuart Mill.
Frankly it's difficult to know which to feel more strongly - outrage at the anti-liberal character of Huhne's suggestion in his opinion piece or shock at the simple-minded nature of his argument.
His argument is no more than this:
In my opinion, Geert Wilders' revolting film Fitna crosses [the] line [into incitement to hatred and violence], 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.
First, there is a huge non sequitur here. Yes, the film does tend to invite very hostile attitudes to Islam by juxtaposing verses from the Koran that appear to demand violent acts against non-believers with images relating to acts of terrorism carried out by Muslims. It's possible, of course, that someone might be inspired by seeing Fitna to take direct violent action against Muslims, but - whatever else the film does - it does not call for this. There is certainly no incitement to any specific violent act or any class of violent acts. Obviously, however the film is interpreted (and it is certainly open to interpretation) it does suggest a very harsh view of Islam and arguably of Muslims as a class of people, but it is Wilder's right to present such a view and it is the right of others to rebut it.
Would John Stuart Mill have tried to suppress Fitna or to have shut up Wilders (or kept him out of the UK)? I very much doubt it.
Mill did not think that the power of the state should be used to stop actions that might produce harm by some indirect process, such as somebody saying something that then leads to someone else harming a third party. He had a very restrictive view of when the state should interfere with speech. His example of when it would be justified was a demagogue addressing an angry mob outside the house of a corn dealer, inciting the mob to lynch the corn dealer, on the basis that "corn dealers are starvers of the poor". But Mill would not have accepted censoring the claim that "corn dealers are starvers of the poor" if it appeared in a newspaper (or by implication a book, or a film, or whatever).
Huhne must know this, or at least he affects to be familiar with Mill's thought. But he does not think it through to realise that Mill would not have favoured censoring Fitna, or, in most circumstances, suppressing Wilders' freedom of speech.
Here's how I think Mill would see it. The state would be justified in (1) stopping Geert Wilders from addressing an angry mob and stirring it up to lynch nearby Muslims. But the state would not be justified in preventing Wilders from (2) entering the UK and putting his views peacefully to the general population (this includes giving a lecture of the usual kind which is not directed at inciting a riot or a lynching). Nor would it, on Mill's account, be justified in (3) banning Fitna.
In case (1), there's no time to respond to the situation other than by stopping him and dispersing the lynch mob. The state needs to have laws to deal with these situations.
In the other cases, cases (2) and (3), Wilders' views can always be argued against; individuals are not caught up in the mentality of a mob, but can think calmly if they are so inclined; any individuals who just might be inspired to lawlessness can be deterred in the same way as any other individuals who are inspired to lawlessness by anything else that might have the same effect (reading a holy book, watching the news, listening to rap music, or the whole gamut of activities that can get people steamed up), and so on. In summary, cases (2) and (3) are remote in every way from the kind of circumstance where Mill would consider the use of state coercion to stop someone's free speech to be justified.
Mill is very clear about this. He spells out that the harm principle is all about direct harms, and that the use of state coercion to stop something not directly harmful is an absolute last resort. He'd count the corn dealer example as direct enough, or as a case where there is just no alternative to state coercion, but he would not generalise it to allowing censorship of the media. He would not extend the example to situations where the imminent prospect of violence does not exist ... and nor can Chris Huhne if he wants to be a good Millian liberal.
I should make a final point before I'm accused of being simplistic myself. With modern technology, there can be situations where speech can incite sufficiently immediate violence even though there's no physical proximity between the speaker and the target of the violence. If there's enough anger or hatred through a community to put potential victims in the way of violence from angry attackers, there can be situations that are relevantly analogous to the corn dealer example. Imagine that the day after the September 11 attacks a popular radio shock jock had declared to an audience full of para-military militia members, "That's it. Get your gun and kill a Muslim now!" This would be getting closer, in the relevant respects, to the corn dealer example. Likewise if someone had been able to send out the same message by cascading texts to the mobile phones of 1000 testosterone-soaked young men who were already known to be armed and to hate Muslims.
I'm giving hypothetical examples here, but of course there have been real examples not far from these. I'm not such a free speech absolutist as to deny that such examples happen, and laws are needed to deter them.
I'm certainly not saying that there can never be cases that where the risk of violence is sufficiently high and imminent for some kind of state action to be necessary. I even acknowledge that it may be difficult to draw a practical line when laws are framed, so a law against inciting violence might have to be drawn more widely than Mill would have approved of. Indeed, I'll go further and say that, although I think Fitna falls clearly on the "don't ban" side of the line, there could be doubts about what Wilders just might say (e.g if interviewed by a shock jock) - he does seem volatile. Sometimes he appears to be testing the tolerance of even liberal-minded people. For that reason, I feel little sympathy for him as an individual.
But Wilders has been in the UK before without stirring up lynchings or riots, and I see no evidence that he has ever crossed the line into any kind of clear incitement that should be cognisable by the law.
And even if a case to the contrary could be made out, it would need to be something far more sophisticated than what poor Chris Huhne offered in his weak excuse for an opinion piece.