If he said we need to figure out "how this outrageous attack took place" (and not "why?") then he's right. There was obviously a security breakdown that allowed this to happen.
I know Obama's an idiot, but this quote is not a good example of it.
But he didn't, he said "why".
As to a security breach: This was at a public airport, not on a military base. Outside at that airport. You gonna screen all the people coming onto the airport grounds now. Check their private area for hidden guns or explosives?
You can't defend everything and every place against small scale attacks. You just can't. You have to go to the source of the attacks and take that out. And that's a very big job in this case, since that's a big chuck of the world population that these folks come from.