Gracchi has a brilliant post up on Inayat Bunglawala's rather inconsistent attitude to free speech. Turns out he's all for defending people's "fundamental right to say that I want to bomb you, [their] fundamental right to download materials from the internet about bombing and to write poems about how nice your brains would look if only they were blown from your skull" but not so keen on allowing any criticism of Islam.
Combine that with Perry de Havilland's excellent fisk of Dr. Abdul Bari's interview with the Telegraph and you have a pretty decent primer on the MCB's contribution to the national debate.
For an examination of their more 'practical' contributions to extremism you'd need to watch the excellent Panorama on the subject (this is an online version but I think it is similar enough to the original broadcast). The programme doesn't follow its lines of inquiry through to their conclusion but it should be pretty obvious how deeply unsatisfactory Sir Iqbal Sacranie's answers are.