I didn't provide any evidence because I haven't got the research to back my claim up. The only way to gather real data would be to publicly proclaim some random blocks of calendar dates to be TSA free and see how much tourism changed during that time. I'm sure it would be interesting to see how much terrorism changed over that period (any effects would probably be exaggerated).

I can tell you it affects my personal travel plans (I try to avoid a stopover in the US on the way from NZ to London for example) and it makes me feel more negatively about the US overall. It doesn't take much to tip the balance from "I'd love to go" to "I'd like to go, but xyz location seems easier / more fun"

Since I live outside the US, I have an actual choice - if you lived inside the US you are pretty much forced to tolerate the TSA whenever you fly. I read a lot of horror stories online, and I don't like being near people with sidearms.