The purpose of terrorism is to provoke an overreaction. Its real aim is not to kill the hundreds of people directly targeted but to sow fear in the rest of the population. Terrorism is an unusual military tactic in that it depends on the response of the onlookers. If we are not terrorized, then the attack didn't work. Alas, this one worked very well.
Overreacting to terrorist attacks plays into al-Qaeda's hands. It also provokes responses that are likely to be large-scale, expensive, ineffective and possibly counterproductive. More screening for every passenger makes no sense. When searching for needles in haystacks, adding hay doesn't help.
I don't have much to add that I haven't already said, but his whole piece is worth reading. The man knows what he is talking about.