The hard bit is deciding where the line is drawn. With Northern Ireland, Sinn Fein were not invited to sit down with officials because the boundary between them and the IRA was not clear. And if Hollywood has taught us one thing, it's that we don't negotiate with terrorists.
So, in the current situation, they can invite people who are obviously not associated directly with the terrorists, but inviting activists blurs the boundary somewhat. There are probably plenty of groups made up of young muslims who shout about how they hate the decadent west, and how they were so happy to see airliners fly into skyscrapers, but they would never consider blowing themselves up over it. This is where the grey area lies. Sure they are not terrorists themselves, but they agree with the motives of the terrorists or even approve of terrorist actions.
Whilst it's always useful to find out WHY someone has a particular view, sometimes it isn't a good idea to lend credence to that view by acknowledging it might be a valid view.
I read somewhere that young muslim men are underachieving in this country. All the muslims I know are systems analysts, consultants and junior doctors. Perhaps that's why I never encounter radical views!
So, how do we ensure young muslim men achieve their potential? I've always believed that self-segregation will lead to problems, and I should point out that all those successful muslims I know went to comprehensive and grammar schools (not muslim schools) and also live in "normal" areas (i.e. not highly concentrated muslim communities). They are still practicing muslims, one of the junior doctors is actually quite devout Sunhi, you can find a mosque in any town and my company has a muslim prayer group who all go and pray together at lunchtime. But they obviously feel no need to shut themselves off from the rest of the UK in order to fully embrace their own religion.
So, I think that the problem will reduce or even disappear if we can fully integrate these communities.