You can't outrun a car-bomb explosion any more than you can get off a plane mid-flight. Statistically, you're much more likely from a terrorist attack on the ground than one in the air. Yet we don't engage in these kinds of searches in other many other places that are at risk. You don't have to go through a backscatter x-ray when entering a shopping mall, or getting on the subway, or entering a crowded public area.
I don't oppose reasonable measures to secure airplanes. I oppose unreasonable, ineffective ones. Taking off my shoes for airline security is annoying, but I don't have a problem with it, because it's merely an inconvenience. I haven't seen any convincing argument that these machines are effective or reasonable. The items they're looking for that pose a threat could easily be detected by other existing, less invasive means, such as explosive sniffing dogs and machines, metal detectors, etc.
The difference between myself and someone like Microsoft Windows on this topic is a matter of degree. I would agree broadly with many of his ideas of what is reasonable airline security, and disagree with a few on practical and philosophical grounds, but I'm sure he would find many hypothetical measures unreasonable.
Wellington, on the other hand, would submit himself to any restriction or humiliation if the government said it was necessary. He's said that he would accept body cavity searches, or being shackled during the flight would be reasonable, if the government said it would prevent a terrorist attack. And he seems to think his point of view is a liberal one.
"Voice or no voice, the people can always be brought to the bidding of the leaders. That is easy. All you have to do is tell them they are being attacked, and denounce the pacifists for lack of patriotism and exposing the country to greater danger. It works the same in any country."
-- Hermann Goering, second in command of the Third Reich
That's right, I'm going the full Godwin.