Actually, I don’t disagree with his assesment, I’ve said the same myself, however, when you can kill hundres of innocents at one blow, does it really make any difference what their motivation is?
Well, if the thing that motivates them is something you did or can control, then it makes a big difference. By being aware of such (and not ignoring the warnings), you can prevent or react appropriately.
In the case of the WTC, it was pretty durn obvious that we'd ticked them off for being in SA (they told us so), and that they were willing to act (gee, didn't anyone notice a bomb in the WTC in '93?)