We are all sinners and all sins are the same in the eyes of God. So for us to label some people as "evil" is really irrelevant. We all come up short. And forgiveness can change the way people act: Paul says in his letter to the Romans-
Dearly beloved, avenge not yourselves, but rather give place unto wrath: for it is written, Vengeance is mine; I will repay, saith the Lord. 20 Therefore if thine enemy hunger, feed him; if he thirst, give him drink: for in so doing thou shalt heap coals of fire on his head. 21 Be not overcome of evil, but overcome evil with good.
How powerful would it be if we could forgive violent acts against us without responding in kind. If we could hold our beliefs even in the face of injury, loss, and death. Instead of abandoning them under the justification of "well, they did that to me, I should be able to do the same in return."
God tested Abraham by asking him to sacrifice his son for Him, and He tested Job by killing his family and taking all his earthly possessions to see if he would remain faithful to God's teachings. What if 9-11 and all this terrorism is a test to see if we will hold true to the teachings of Jesus or if we will just fall to the same level of violence and destruction that we claim to abhor? We dont seem to be doing a good job, especially since we have a presedent who claims to be a Christian who talks to God daily. I saw a bumper sticker the other day that asked "Who would Jesus bomb?" Damn good question huh?