Like I said, I appreciate your point in general, and I would even go so far as to say I agree with it: discerning the motives behind terrorist acts could indeed aid in preventing future attacks. That said, however, I would repeat that in my opinion, an attack of this nature, on such a huge scale, can not possibly be justified...ever...so the terrorists' motives, whatever they may be, are of no concern to me, except where an examination of the motives may help identify the guilty parties.
Anyway, I sure don't want to argue with anybody. This is a time for us all to unite and extend our sympathies to all the victims and their families.
Peace be with you!