Should be noted that dogs would probably do a better job at a fraction of the cost.
Should be noted that terrorists generally have an IQ above 40 and can get around this easily. "Slippery slope" is not a fallacy here unless you can tell me exactly where the line on invasiveness will be permanently drawn. Because I guarantee you that wherever you draw that line, terrorists will cross it. Still, you must draw it. I refer you to the constitutional amendment against unreasonable search and seizure.
Should be noted that you are much, much more likely to die in a car crash, yet I bet none of these "pro-safety" people would like to be told they have to wear helmets while driving, or that they can never drink again because some people who drink become drunk drivers and kill more people than terrorists.
Should be established what you will do with people who refuse to go along with this. "Don't fly" is a hypocritical solution. Planes can't serve peanuts because a few people have peanut allergies. Well, some people have very good, proven reasons for being afraid of invasive, uncontrolled authorities. Ever had someone lie about you to airport security? It's a great way to get back at your enemies if you have absolutely no ethical standards.
Yes, in fact, I am okay with a 1 in a million chance of being blown up. At least it would be an interesting death. This is authoritarian, and in my opinion, the lives of willing citizens of an authoritarian state have somewhat less real value than the lives of free people. If you think I'm talking about you, deal with it; you were going to be pissed off by this post no matter what. If you think that's racist, fine, go ahead and think that. But I doubt citizens of full-fledged police states are as worried about 1-in-a-million risks as Americans are. Physical security is over-valued in the US, and the terrorists know it. They're not trying to physically destroy us; they know they can't. They're trying to destroy our power, and our power is based on mutual trust of other civilians and a willingness to take reasonable risks. That's definitely true of the economy and I say it's true politically, too. If you sacrifice liberty and dignity for a 0.0001% unproven, temporary improvement in physical security, what exactly are you protecting?