That would mean we would wait until AFTER they had blown stuff up or crashed vehicles into things before attempting to do anything to them.  And given that many of these missions are suicide missions to begin with, that would largely mean that the government would just shrug its collective shoulders and say,

"Well, it's kind of sad about all these dead Americans, and the billions of dollars of damage to the economy, but these bad guys are all dead, so at least *they* won't do this again.  Now move along, nothing to see here."

It would mean NO preemptive action against those whose stated desire is to kill Americans down to the last man and totally destroy our society.  And if none of the earlier attacks proved it, 9/11 finally proved that they were capable of much of what they intended.

-Troy