The problem that we have is that far too many Americans see the things that make these lowlifes really stick out as things that we need to just tolerate more. Too many Americans think they just need to understand these people more, as opposed to being suspicious of their behavior. Just look at the woman from Dept of Ag. that was approached for a loan by Mohammed Atta. She said that his threatening her life, demanding cash so he could build a cropduster, throwing money on the desk demanding the photo of DC, etc. as just cultural differences that she just needed to be more understanding of.
These people are typically dumb as rocks but unfortunately the PC crowd has brainwashed too many Americans to overlook the obvious so that it probably works in their favor. We were lucky that in the first WTC bombing back in 1993 that the clerk at the Ryder truck rental place was alert enough to contact police when the brain surgeon came back for the deposit on the truck he had just blown up. If the terrorist back then had the sense to just not go back, we probably never would have caught any of them. The more outrageous the behavior, the more we aren't supposed to notice.