A group of Saudi intellectuals and academics at a forum organized by Asharq Al-Awsat in Riyadh dedicated to Saudi-US relations after the 9/11 emphasized the need for the Kingdom of Saudi Arabia to answer the question "Why 15 Saudis were among the 9/11 highjackers?". They said that this was necessary "not to please the US but to increase its own [Saudi] national security".
So why, after 18 months after the event, people still find it difficult to answer that question?
The answer is "politics!". Politics makes some simple questions difficult or even impossible to answer.
In this case politics is not as malevolent as politics often is, it its not aggressive, but defensive. Those at the head of the Saudi society understand that the US has considerable military might and they do not want this might to be used against the citizens of their country. This is certainly not a malevolent intention. Nevertheless it makes the task of answering that irksome question difficult.
But, if, for a moment to forget about the US military might and all the connected politics, then the answer to that question might be quite simple.
So, why did the 15 Saudis joined the highjackers?
Many Arabs and Muslims and increasingly Europeans and even Americans themselves see some American policies as aggressive and unjust. Saudis are both Arabs and Muslims and they have a natural sympathy with other Arabs and Muslims, especially if these other Arabs or Muslims are seen as victims of injustice. This is why they have strong feelings about the injustices committed by the Israelis against the Palestinians and against other Arabs and Muslims around the world. And they see the Americans as the supporters of Israel. So, this is one source of anti-American feelings.
The other source of anti-American feelings is the behaviour of the Americans in the KSA. The American military bases, the American values (alcohol, nakedness, sexual promiscuity, homosexuality) are in sharp contrast to the traditional Arab and Muslim values. It is true that not all Americans, and probably not even a majority of the Americans share these "American" values, but, unfortunately, people tend to generalize and "paint them all with the same paint1".
Of course, not all Saudis having such feelings become terrorists and attack Americans. But, it is not surprising that a small number would want to take some active steps to fight what they see as wrong.
A tape attributed to Osama bin Laden explains in details the motivations for anti-American terrorism as seen by Osama bin Laden supporters.
So the answer to the question of "why they did it?" is quite simple - they see Americans as the enemies of the Arabs and Muslims.
The more important question, however, is "How to prevent acts like the 9/11 happening in the future?"
The difference between terrorism and ordinary crime is that terrorism has a moral justification. This justification can be right or wrong, but the terrorists believe it to be right. It is this belief in their own righteousness that makes them sacrifice their own life. They might be wrong, dangerous and harmful, but they are not "evil", at least not intentionally so. In fact, their intentions are to destroy what they see as "evil".
The way to prevent terrorism is either to show to the terrorists that their cause is wrong, or, if their cause is right, to provide a peaceful way of satisfying their just grievances. This should be done not as an accommodation of terrorist demands, but as an enforcement of justice, which should have been done anyway.
So, the first step is to determine, whether the injustices, which the Saudi terrorists sought to redress were real or imaginary, and, if they were real, then whether there were any peaceful means of redressing the injustices which they should have used, rather than resorting to violence.
Unfortunately, one has to agree that the grievances which motivated the terrorists, that is the injustices inflicted on the Palestinians, and the American arrogant policies and politics, are real. So, to deny or ignore their existence will not dissuade any future would be terrorists from resorting to violence. So, the only option left is to seek peaceful alternatives to terrorism, which will make violence unjustified.
One of the obstacles to resolving the so-called Middle East Conflict has been failure to clearly state its causes. Instead, vague solutions have been proposed - like creation of a Palestinian State. While creation of a Palestinian State can be part of the solution, unless such measure will remove all the causes of the conflict, the conflict will not be resolved.
The other reason why the conflict has not been resolved up to now is the belief that issues involving injustice can be resolved by negotiations or agreements between politicians. This is an erroneous view, because, no matter what the politicians agree between themselves, unless this agreement will remove all the causes of the conflict, the conflict will not be resolved, because, if the injustices remain unredressed, and the victims of the injustices, or their sympathizers, see no ways of redressing their grievances by peaceful means, they will resort to violence and the conflict will continue.
Thus, the only way to prevent terrorism in the future is to establish workable means of resolving so-called conflicts (or, more correctly, the consequences of crimes against person and property committed by governments) on the basis of justice, rather than by political horse trading.
This can take a long time and much patience and perseverance, but this is the only way.
The other source of anti-American feelings - the conflict of values, should be approached not by seeing the Americans as the enemies of Islam, because they are not, but as ignorant, miseducated, depraved people, because this is what they are. They need help and guidance, not hatred. Contacts with Americans should be welcomed, not shunned, and used to enlighten, educate them, and, yes, to civilize them.
1) Such generalizing is not specifically Arab or Saudi - some Americans attacked Sikhs (who are not Muslims) after the 9/11, because they wear turbans and have beards.