Threat from self-delusion:
The monster of Norway, the Unabomber, the Oklahoma City Bomber, and the pilots of 9-11 airplanes all suffered from two extreme self-delusions:
a. That their actions would cause what they believed would be “positive global” effects,
b. That they were fulfilling a calling, a destiny for greatness, and would be admired/remembered for their actions.

Threat from rationality:
a. Our collective self-delusion that the world is or can be 100% rational – that the actions of madmen can be rationally explained and thus be somehow prevented in future.
b. No single person can carry out such madness, therefore there must be some secret group behind the horrendous act(s).