To kill or be killed is defensible, however, killing people who hate you does not stop terrorism. For with the death of each terrorist, you alienate family members and friends, creating even more hostility against your cause.
We are all interconnected, and so as a global family, there exists an endless number of people who can, and will oppose your attempts to eradicate them.Who in their right mind is prepared to fight the whole world?
Death is not a deterrent to a person with a just cause, and killing is not a viable substitute for good negotiating or problem solving skills. As a society, people need to rise above the desire to eliminate a problem, by eliminating the person.