I'm wondering about the above highway patrol analogy, with the hint that we could not do without such a police force, therefore validating the TSA.
How many people are killed on our highways every day...every single day? So we use the abstract argument about how many more would be killed were it not for the highway patrol?
...
Theoretical similar mission creep: The highway patrol just knocked on my door because they want to inspect my cars parked in the driveway. Saving lives, ya know.