The fact that some mass murderers are crazy, is not a free pass to paint all mass murderers as such.
Conversely, the fact that some mass murders are not "crazy" (depending on your definition of "crazy" 
) is not a free pass to paint all mass murders as sane. 
Which makes it very difficult to assign blame in cases where there is no direct link between the terrorist and the supposed terrorist organization.
What prevents someone with mental problems to follow "the al qaeda open source cookbook" for his own reasons? How do you assign blame? If the person used a scene from a movie (e.g. "The Dark Knight") to commit an atrocity, does that mean he was trying to advance the politics of the movie? If he used a scenario from a novel, does that mean the killer was trying to advance the politics of the author? Would arresting the movie producers or the author help prevent further attacks?
If an organization provides direct support to a terrorist, then there is little question that they are to blame. But if they just publish some instructions and someone with mental problems uses those instructions, eliminating those who published the instructions would do little good to prevent further attacks, unless you eliminate all such instructions from all sources.
wayward, are you being intentionally obtuse, or do you not understand the difference between causality and blameworthiness?
If you never had the chance to learn the difference, then you are blameless for saying something so foolish.
If you've had it explained to you before, but chose not to pay attention, then you are somewhat to blame.
If you really do understand the difference, and yet played stupid for political purposes, then you are very much blameworthy.
Similarly, if the Dark Knight producers intended to inspire copycat murders, then they are to blame.
If they did not have and could not reasonably have forseen that it would inspire copycats, they are blameless.
The fact that folks imitate the stuff in the open source jihad books shows causality.
The fact that the open source jihad books explicitly intend people to follow them, means that one should reasonably assign blame to the organization that publishes them with that intent.
Finally, the fact that there is offer (promise of eternal life) to those that follow said cookbook, and acceptance via committing the act, creates a contractual connection between ISIS and nutball.
for you to deny that there is a connection, is as stupid as claiming that there's no connection between Khomeini offering a bounty on a writer's head, and an assassin trying to kill said writer.
