The people really responsible are the 'colour blind' politically correct establishment that refused to stamp the extremism out when it first reared it's ugly head same with the Rochdale pedophile gangs and the others.
We weren't PC when dealing with the IRA and we smashed them and changed their leadership structure through selective arrests (and taking out the wrong people leaving the 'right' people in charge) yet some how the government have been scared to do anything about the Muzzie version of the same thing.