So any measure that isn't perfectly effective should be discarded? What perfect security methods do you propose?
The best security we have is the determination of a free people not to be flown into buildings again.
Why is it wrong to try to protect people from having to make that choice? If the fit hits the shan, I'll be right there alongside you, fighting to take back control of the plane. If that means we go down rather than hitting a building full of innocents, so be it. However, I'd really prefer not to have to make that sort of sacrifice in the first place. In exchange for a reduced possibility that I will be inconvenienced when my plane slams into the ground at 300 mph, I accept the somewhat smaller inconvenience of consenting to a search before boarding. Others may prefer not to be inconvenienced at all - for them, there is Greyhound.