It seems now days that some mentally challenged reactionary conservative would commit an act of terrorism rather then a liberal or socialist/anarchist, because conservative thought becomes relatively more old and rigid, becoming overwhelmed by the progressive aspects of society that flow naturally thus reacting in such a way violence sometimes seems the answer, in the case of the new left that's not the really the case because evolution is welcomed, even tough violence exists within the new left, that violence limits itself to useless riots,black blocs etc. not killing sprees.

I thought about this myself while writing the first comment on this thread, there is actually a whole concept in the anarchist tradition that promotes physical violence against political enemies, its called "propaganda of the deed" here it is http://en.wikipedia.org/wiki/Propaganda_of_the_deed . Propaganda of the deed, as a violent form of direct action involving bombings and assassinations, was abandoned by the vast majority of the anarchist movement after World War I (1914–18) and the 1917 October Revolution. There are various causes for this, but important factors include state repression, the level of organization of the labour movement (in particular the new importance of anarcho-syndicalism in European Latin countries such as France, Italy and Spain) and the influence of the October Revolution. Anarchists pretty much abandoned propaganda by the deed when anarcho-syndicalism became a major tendency within the movement, and about propaganda of the deed in general, we must think in that era and age, we are talking about fighting inside near a totalitarian state it is acceptable to use violence in such a society in my opinion, Alexander Berkman himself abandoned terrorism stating that in his book called "What Is Anarchism?" you can check it out plus we can understand Berkman and the terrorist tendency of the late 19th century and early 20 century this tendency actually appeared out of state repression so we can't compare the 19th century or 1900's with the 21 century.

these people that kill random doctors and innocent people are MENTALLY CHALLENGED in my opinion, the 9-11 hijackers were mass delusional and mentally challenged too, no one in their right state of mind kills innocent people in such a way, maybe i am naive but i still think human society is civilized enough to stop acting like this. Anyone that does such acts are mentally challenged in my opinion.