Civil Protest over Violence
The notion that violence is the only means of achieving beneficial social and political change is fallible, thus wrong. History has proved from era to era that change exacted through violence is plagued with complications and stagnation of real life prosperity when it is gained through the sword. The rise of the communists in Russia, China and North Korea, are examples.
However, peaceful civil protest by the people as an alternative to the use of the cult of violence, appears to offer a greater hope and a more enduring effectiveness to beneficial change rather than any resort to violence. The accomplishments of non-violent movements are known including that of Dr. Martin Luther King, Jr., in the United States(US).
Therefore, any credible grievances terrorists might have with normal society could be addressed through civil protest instead of violence, but that has not been the case because terrorists have demonstrated from violent event to violent event that their actions are vile and rooted in a selfish political agenda convoluted in religious dogma.
Hence, all acts of terror are bad and wrong and all terrorists are criminals. The full weight of the law must always fall upon any and all persons perpetrating violence upon the serenity of innocents.