Let's also not forget that airports and airplanes have a bizarre way of turning otherwise normal, sensible people into drooling and/or belligerent idiots. A guy with a doctorate can step out of his car, pick up his luggage, look at an airport, and immediately forget everything he has learned since kindergarten. It's strange.
I worked in an airport, and I still fly frequently for work, and if there's one thing that I'm absolutely sure of it's that I do NOT want the general flying public to have access to anything that is designed to function as a weapon. Nevermind the drooling idiot factor - speaking as a person in law enforcement, the average member of the general public is useless in any type of high-stress conflict scenario. Worse, wannabes are a hindrance to those who actually know what they're doing.
There is a really simple way to keeping the peace on aircraft - one or two highly-trained, professional, and unarmed (except for perhaps a Taser) plain-clothes security/police personnel on each and every commercial flight. It'd be cheaper than bodyscanners in every airport, you could reduce screening to a person-based rather than luggage-based affair (Israel has got this **** right), and would be less hassle for everyone involved.