When you have limited human and/or other resources you don't check a white woman's child just because... you know why (!)... you check Muhammad (plus his wife, and their children).
When you're a terrorist and you see the TSA feeling up Muhammad and his wife and children because of how they look, you naturally find a Robert who won't be searched because he doesn't look like Muhammad or his family.
What then? You'll start feeling up Muhammad and Robert and their families? What about David?
What about Elias who belongs to a completely different group and has a completely different mission than destroying a plane or building? Say he just wants to assassinate a specific passenger.