It is easy to get caught up in the geo-political reasons and responses surrounding September 11th and forget the ultimate cause of 9/11, the Holocaust, the Soviet purges, the Killing Fields and every single time man kills man, from Cain and Abel to World War II to the streets of Chicago. The reason is the same, always. Man is dead in his sins until and unless acted upon by the Holy Spirit. People don't kill each other or steal or rape or beat one another because they don't have enough job training programs. They do all of this because it is their unregenerate nature to do so and not only that but they love the darkness. People don't hate Jesus because His followers are sometimes/often jerks, they hate Him because He is the light of the world and he exposes their works as evil. Men love evil and love to hide their evil in darkness as if they can hide from God but they cannot. The light of Jesus exposes all of their evil.
We can never overcome evil by the sword. Evil can only be overcome by the life transforming Gospel of Jesus Christ, one lost soul at a time.