As I see it, the greatest deterrent against extremism would be for suicidal terrorists to be told that it is very doubtful indeed that they will go to paradise when they die. Most Muslims believe that it a sin against God/Allah to kill. Many are prepared to die because of an incorrect assumption. I wonder how many would be prepared to die if a hell awaited them? Not many I expect.
They should not assume what they do is "in the name of the prophet" as it is not.
The world would be such a nicer place if everyone could live in a state of mutual respect and fairness. We are all different but all deserve the right to freedom, happiness and peace. It is usually an accident of birth what religion (if any) we follow. Some Jews could just have easily been Muslims and vice versa.