The point isn't the lack of security but the test of a 747 hull versus explosives. Security will always be needed as will the advance in technology to detect such devices, but what the test did show was how strong the fuesalage actually is - hopefully detering in some way future (similar) attacks. If the results of this test increase public confidence in flying that can only be a good thing for the future of aviation!
Great theory but it won't work.
We are dealing with general ignorance at the public's level. Blowing things up just reinforces their fear that they are at risk from even their seat mates. We certainly aren't going to educate the bomb makers who know how to capture the publics attention with the tiniest of bombs even if all they do is blow there own nuts off in the middle of the inflight meal.
Those in aviation already know how tolerant the aircraft is or isn't so we didn't need the test. This is all
PR and the bad guys will always win at this with their next trick even if it's all smoke.