Poll: Should Muslim extremist groups be banned or debated?

Recently there have been several suggestions that groups such as Hizb ut-Tahrir should be debated, rather than made illegal.

Ed Husain, a former British member of Hizb ut-Tahrir, originally called form to be banned, but later changed his mind:

In the past, I've called for them to be banned. However, in recent months, several leading former members of HT have come forward and formed a network that now is able to challenge and easily defeat HT's arguments using scripture and theology. This is unprecedented in Britain. Most prominent among these former members is Maajid Nawaz, who spent four years in an Egyptian prison for his membership of HT. Now, as director of the soon-to-be-launched Quilliam Foundation, he has openly challenged HT to a public debate. To date, they have shied away and their supporters have resorted to character assassination. When as Muslim democrats we can defeat HT with arguments, why should we resort to a ban? I am convinced Maajid's method of open debate is better than driving them underground. It remains for HT to respond.

Muhammed Hee, a Danish Muslim convert and former member of Hizb ut-Tahrir, recently said the same thing (Danish):

He doesn't think that a ban against Hizb ut-Tahir stop members' attempt to radicalize others, but calls instead on moderate Muslims to go against Hizb ut-Tahrir in the public debate. At the time he warns Muslim families and social authorities to be on watch for Hizb ut-Tahrir's attempts to recruit young Muslims to the party.

Dutch politician Geert Wild has now invited some of the Netherlands' most extremist imams (Dutch) to a public debate: Fawaz Jneid of the As-Soennah mosque in The Hague, Mahmoud el Shershaby of the El-Tahweed mosque in Amsterdam, and Ahmed Salam from Tilburg. Wilders had tried to deport them in the past, and now says that you can only conduct a debate with those who think differently.

What do you think? I have put up a poll at the top of the right hand side bar with the question: Should Muslim extremist groups be banned or debated?