Earlier quoted context omitted.
The TSA detained the man (possibly illegally), called the police, threatened him, and ultimately only acknowledged their bad behavior under the threat of a lawsuit. If that's reasonable, I'd hate to see unreasonable.
I'd say "unreasonable" is not answering the reasonable, banal questions of people employed to protect travellers and the nation at large.
Protect from what? Cash isn't a threat and it isn't contraband. $5k is only half of what it takes to raise bankers' eyebrows, and they're at least qualified to investigate money laundering. The TSA goons had no defensible reason to waste this guy's time, much less go on a fishing expedition into what's usually intensely personal affairs.