To be honest, beyond the very rare thief that crops up in all of Society, the TSA guys are probably just doing what they think is their job and they are honest folk - just like the Customs guys over here. Their bosses put them under immense pressure not to let anything through that might come back to haunt them and they know that your average Joe Public won't argue back and won't complain or take it up with their bosses ... so they are safe to confiscate even the very borderline things. They look good because their bosses are happy ... their bosses look good because the airport appears to have a good record and bucket loads of seizures to show Homeland Security.
Customs will go to inordinate lengths to seize whatever they can because they know that nobody has got the money to take them to Court and call their bluff. I am sure they, like the TSA, will have appeal procedures and if you appeal they will probably reject it and force you to take them to Court ... end of story.
It's a bit depressing but the only way to get it to change is to direct your attention higher up the food chain to the politicians that give these guys the powers they have.
My spydies: Squeak, Tenacious, Terzuola, D'Allara, UKPK CF peel-ply pre-production, UKPK CF smooth pre-production, UKPK G10 orange leaf-blade, UKPK FRN grey drop-point, UKPK FRN maroon leaf-blade, Bug ... all PE blades