And given the number of test firearms that the TSA manages to get through the carry-on X-ray, it'd hardly be reassuring even if the full-body X-ray turned out to be useful.

Completely agree. But that's a different issue entirely - arguing that it's useless because it's not part of the flight is complete nonsense.

You still don't make any sense. Here is activity A: flying. Here is activity B: walking through a Rapiscan machine.

One can do activity A & B independently. One can board a plan and fly ( I just did recently, got into a line that didn't have an x-ray machine and flew). Or one can do B -- keep buying tickets and go through security without flying and just do that all day.

Now the argument was both activities will blast you with x-rays so at least "logically it doesn't make sense to complain about one but not the other". My comment was that it is not the same, there is a difference. I am willing to engage in activity A because that gets me from one place to another faster. I am not willing to engage in activity B because I get nothing for it. You said it yourself it is security theater, so I get nothing but harm from it. Therefore it the two activities are not the same.