In my opinion nothing justifies violence, not even freedom. Ghandi is a great example, who through being prepared to fast to death had it been necessary, ousted the English from India. He chose love and self-sacrifice over violence. He said, "I will never raise my hand against anything alive and I will make the truth triumph without violence," and he succeded.
Those who use other means, (I am implying world powers who believe they are exemlary) go by this slogan, " we will punish violence with violence and solve the problems by sending bombs over the populations." It is definetly a sticky sort of logic because once we have started slipping down the slippery slope it is hard to stop. Once we have started, we must justify the unjustifiable: if we have killed so many civilians until now, then we must kill even more to justify that we were right, because stopping requires more wisdom than not starting in the first place. So we continue in the endless cycle of terrifying logic.
Violence never solves anything. Never. Violence leads to more violence. Once it starts, it dosen't stop, and when we step in and get involved, we are obligated to carry on even more.
Non-violence is far superior to violence and always wins. You have to be patient though. It's true that some people died defending this principle. The first Buddhists were killed , but Buddha's message still got through, The first Christians were fed to lions, but Jesus' message still got through. The first Muslims were persecuted, but the message of Muhammed still got through.
If our history books had been written right, they would include hudres of pages on Gandhi, Buddha, and Jesus and they would mention all the people who worked for peace, and only devote one page to the crimes of Napolean, Hitler, Julius Caesar and Attila the Hun. Unfortunately, these criminals are all portrayed by some as heroes, and their heroism is based on violence and only violence.
Using fear to bully someone into suBathmateission is the ideal definition of terrorism. Those in power are under the allusion that they can solve terrorism through violence.