Yes, but you have to think further. Think beyond that ! Don't look at it from a one-dimensional perspective.
If everyone on earth was evil. They wouldn't be evil, but normal. Amongst those that are evil there would be people that are less evil and those could be considered good.
Without "evil terrorists" there would be something else that would be the most "evil" in this world. It's all a matter of perspective. It is a very interesting phenomen in todays society. Just watch a movie and see that you sympathize way more with the protagonist no matter if they are evil or not.
Good and Evil are understood by our perception of society. There is no universal good and evil. There is no concept of good and evil that transcends our human understanding of it.
There will never be true global peace and harmonry on earth. It is impossible. First and foremost because people have a different definition of what that actually means. Even if you find a way to end terrorism there will be something else that people claim to be evil. Maybe the media makes mexican drug gangs responsible for everything bad in this world. Who knows.
I agree that the world should fight terrorists, but I disagree that innocent people should be harmed. At what point do we become evil without realizing it and just claiming our deeds as a lawful good act?