If anything, this is an example of a situation in which talking to the cops is actually your best option. If he'd sullenly plead the 5th there's a good chance they'd have arrested him properly and maybe even charged him, causing him to miss his flight.
I can admit this sounds like a fairly unpleasant experience, but airports are high security, unpleasant environments. I'm still not sure how someone could accidentally take a tip jar despite paying with card. Did he black out for 30 seconds?
"It’s like: my accusers arrive on the scene committed to a specific, hostile theory of me: that I’m a petty thief of smoothie bars, let’s say, or a sexual-harassment-loving misogynist."
But he did take the smoothie bar money. He might not have realized he was doing it, he might not have done it on purpose, but he did take the money. In this metaphor, he commits sexual harrassment but it's ok because he's too gormless to realize what he's doing.