Well said Kolmo.
I would add that it is human nature (genetics and evolution driven) for male physical aggression. Generally speaking, we (men) are programmed with a strong, sub-consciuos desire to hunt, kill and protect for the sake of food resources, territory and family/clan. Just think to all the news and personal experiences you've had to find truth in this - all fights, wars, rapes, robberies, etc. are, generally, committed by and/or instigated by men. Men with high and variable fluctuating levels of testosterone and watch it get even worse - e.g. roid-using wrestler who randomly killed his family.
This served us well 'back in the day' of living in caves/huts and living off the land, but in the modern agrarian society, there is no inherent need for males to hunt and kill any more. There is no regular, routine outlet for the evolved aggressive tendencies. Without an outlet for this aggression, it seeths under the surface and manifests itself by escalating 'hate' of almost any societal grievance from an intellectual perception to a physical threat and they will use the tools/weapons at their disposal to attack the grievance.
Unfortunately, evolution can't work on the same timescale as human society to get rid of these aggressive tendencies, someday it will catch up as murderers, rapists, etc. are removed from civil society (life in prison) before they have children. Additionally, the 'fattening' of the population will help amerliorate the pent-up frustration as fat absorbs hormones. But this will only moderate behaviour, not genetics, so as soon as society slims down to normal size/weight and their children will have the same tendencies.
We try, as parents, to raise our children to be respectful of others and to suppress their aggression, but on a physiological level, we are fighting a losing battle. We are basically trying to train the brain to control automatic physiological systems, which unless you are into yoga, etc., is very difficult to do. I mean we 'punish' children acting out physically (hitting, biting, kicking, pushing, etc.) to try and reinforce to their brain's that this is unacceptable, and over time and with consistent training we can do pretty good.
But it is always there, the underlying machinery never goes away (until testosterone levels drop with age) and with sometimes very slight provocation, the most mild-mannered guy's control over an emotional, physical response is weakened and, to quote Rummy, 'stuff happens'.
All of the above, in terms of trying to control, train, mitigate male aggressiveness is based on my experiences as an American in the U.S.. Realistically, there are 5.8 Billion other people around the world, the vast majority of which live in deplorable, near 'back-in-the-day' conditions, where this aggressiveness is still a requirement for simple day-to-day survival.
Even in the U.S., we can't control it very well. I think every single boy/man in America understands that if you commit rape, assault or murder you will (98% chance) get caught and go to prison, potentially for life or even be executed (i live in Texas, it's what we do). Yet this does not act as a deterrent, which can be explained by the fact that, again, this is an underlying physiological system that will always be there no matter how much intellectual control we think we have over it.
What does all this mean? Well, it means that there will always be people out there (mostly men) who will feel an overwhelming need to relieve their super-aggression, but have no real outlet and so, if they have the resources, will try to cause harm to others. In most cases, it will be limited to beating family members or getting into physical fights. But for some, this isn't enough or isn't possible, so they see terrorist acts on T.V. and it appeals to them on a base-level. They will create some bogus rationale for it, like OBL's laundry-list of anti-American grievances or McVeigh's list of reasons for hating the Federal government, and plan/plot/execute some terrorist act.
For others, like the Palestinians and Iraqis, terrorist acts are due to asymmetric warfare. They have been provoked and the natural response to defend territory can only express itself with the tools at hand. In Palestine (G&WB), the conditions are extremely dire and throwing stones at Israeli tanks can only do so much to resolve it, so they resort to terrorist bombings, a tool/tactic that does inflict damage to the enemy. Same in Iraq, except on steroids. Through Rummy's bungling and Cheney's denial of proper planning meant we actually armed the populace with Iraqi Army supplies left unguarded - then we disbanded the army's personnel (mostly sunni) with no pay and no jobs and were surprised when these jobless, disgruntled, trained men found out who stole all the armaments and started to use them against the U.S. troops.
Anyway, bottom line is that terrorism as a tactic will be around forever.
Our only response is to attempt to as Roosevelt (i think) 'tread lightly' and try to minimize or marginalize the 'rationales' that these terrorist leaders use as rationales.
But tracking down those few over-aggressive leaders who are able to coordinate and motivate others like them, aka OBL, and arresting/prosecuting them is the only response we have. The more we 'attack' them and cause indiscriminant collateral damage, the more we strengthen their propaganda rationale and thus recruiting.
oh4real