Agreed it is stupidity, but IMHO I think part of the stupidity can be explained beyond just stupidity.

In the case of the TSA Employee who swabbed my car and did not take nicely that I was unconcerned with why he was swabbing my car and his distaste for my comment about the car being dirty anyway and if he wanted he could also wash it as well swab it, I think part of the reason for his stupidity in the way he handle the entire situation was because he felt that I was simply another person to be suspicion of and that I (as well as anybody else) could be the next bad apple, vs. just some guy parking his car at the airport.

Clearly the entire process of swabbing my car seems stupid to me, but leaving alone for the moment, IMHO if he did not see me as a potential bad apple, he might have laughed along with me, rather than said, "Sir, Security is not a Laughing Matter".

I do not know, maybe I am wrong, would not be the first time and surly will not be the last, but I feel that stupidity while a good descriptor does not answer the entire question.

Regardless, there are good TSA Employees, some who are even light hearted, but I feel that part of them being "good" or light hearted is that they understand (either because they have not drank the kool-aide or for whatever reason) that we (the flying public) are people just like them and not some pariah or the next would be bad actor ready to do harm to the flying public.