I suppose STC it could be explained another way. The type of terrorist that this measure is adressing does not want to kill himself/herself, that could be easily done in their own bathroom with their boxcutter. They do not simply want to kill a few passengers, they could do that in the back, they want access to to cockpit.
He or she will kill or incapacitate the flight crew, they will have basic flying training, they will probably have a rudimentary idea of how to program a specific way point into the nav system because they wishes to utilise the plane and everybody in it as a huge cruise missile.
Their mission is actualy quite complex. Yes the odds have been reduced enormously, forwarned is forearmed the threat still exists we know that. Or perhaps you still believe it cannot happen to you. No the threat has not gone away!
Your assumption that it is just some 'yahoo in the back with a boxcutter' is a gross underestimation of the type of threat now around and a dangerous frame of mind to have. No matter how twisted the logic, these people undergo rigorous training and some will be very dedicated to accomplishing their mission and the sooner people like you begin to take them seriously the safer we all will be.