Answer, I like having a stranger feel my "resistance".

Answer: I think my genital herpes has just popped, can you check for wetness?

Because I find the whole thing to be utterly degrading and demeaning and by opting out I retain a little bit of dignity and control. Why should I let a bunch of ex-fast food workers lord their plastic badges over me like some kind of prison guard when I have done nothing wrong? If I'm such a threat, they can find out for themselves.

The health thing is not to be ignored, either, but I've basically quit paying attention to it since I never go through the machines.

To answer the OP, I usually just shrug and say, "Because I don't like the machines."

I've never been asked. But I imagine if/when I am, my response will be something like, "I think the machines are creepy."

It's firm, it's polite, and it's not something they can really argue with (unlike health issues wrt radiation). My only goal at that point is to get out of there, so I'm not inclined to get into arguments.

wg

I prefer dangerous freedom over peaceful slavery

I opt out of backscatter, but not MMW, for health reasons. I had radiation therapy a couple of years ago -- not for cancer, but the doctor in charge of the therapy was a radiation oncologist.

I asked him about the scanners afterwards, and he said to avoid the backscatter ones; the answer didn't give me any context on whether that was in general or given the dose I'd received, but I have always assumed the latter.

Either way, I figure that if anyone is going to be up on the safety of radiation, it'll be someone in his profession. I opt out. I'll volunteer outright that it's because I've received radiation therapy, and my doctor says to avoid them. Usually, that gets me redirected through the metal detector rather than a patdown.

At the same time, with fewer safety concerns about MMW: I have no particular privacy concerns although I respect those who do.

"I'm not allowed any more radiation"

"My arthritis is acting up"

"Those things make my fillings hurt"

"A person always does a better job than the machine"

"My wife/husband" said to"

"You have some really cute TSO's here"

"It's in todays horoscope."

"Nowadays we all have to be careful"