His mosque should be closed immediately and he should be arrested or deported. It is obvious you can't take to these people so stronger measures need to be adopted. All mosques should be closed until the weed out the undesirable elements. It is war...
Remember where you stand on this topic and these events. They will start to blow up things here soon. It will time to take down the muskets and remove these people to their home countries. They can leave, vertically or horizontally --- but they will leave.
There are 3 simple ways to curtail the threat greatly. First, any Mosque in the UK being run by a Saudi Mullah...close it down today, and tell the dude to pack and be out of town within 48 hours. Second, tell the Muslim neighborhoods that if they can't clean up their mess, you will clean it for them, and alot of young Muslim men will spend time in a detention center until they can prove they are "safe". And third, any Mosque that remains open...is absolutely open to anyone, from the private sector to cops...to walk in and observe the situation. If someone is advocating use of violence in the Mosque against any Brit citizen...then close the Mosque entirely. Either they can act cordial in a orderly fashion...or else they can relocate back to whereever they came from. And if they want to claim British citizenship...then they need to act British and be a part of the greatest country on the face of the earth (Winston would have said that...never mind GW).