It is common parlance to hear that we should be free to speak, excepting of course if we incite violence. This has been especially common in the case of Islam4uk, where their defense rests principally upon the fact they have not been involved in promoting violence. Despite its ubiquity, I have never been entirely convinced by this position.
I would suggest that the promotion of violence is arguably not a valid excuse with which governments should be allowed to infringe upon someone’s freedom of association and speech. My objection is both deontological and based on the consequences of banning these freedoms. It is objectionable on deontological grounds because in a free society, people should simply be free to associate and speak freely. Instead of pulling people up for the possible results of their actions, their active part in or association with real violence against others should be the litmus test for infringing upon their liberty.
However, not everyone desires a free society, so perhaps my consequentialist objections could carry more weight. Firstly, it far from clear that there is less violence as a result of people being banned from inciting violence. This might seem counter-intuitive, but by forcing views (however abhorrent) underground, it is possible that more violence might result. It would thus be illogical to ban such groups. Secondly, as history teaches us, there are occasions where violence (particularly against those in political power) was morally defensible. As such, inciting violence is not always morally wrong and it is perhaps best left out of the hands of politicians to decide when it is and isn't.
This is difficult issue, so I would be interested to hear any thought for or against this position.