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?)
The endpoint of this logic is that you submit to their wishes on all things they state opinions about. In other words, you declare them your rulers.
"The way to get what you want is to indiscriminately murder some of us. Do this, and you'll achieve your aims, and increase your power and standing."
This is a really, really dumb thing to be saying. It is what puts every single American under the gun.
It is also what the West has been saying to radical Islam for practically the past 40 years. And that period has not exactly seen terrorism decline.
So, I cannot trust in a leadership position a man who in effect promises to say exactly that to our enemies. Such a man, however much I may admire him on other issues, is a danger to me and mine.