Flying through security checkpoints in the US, I have seen and experienced passengers getting chewed out for choosing opt-out pat-down screening, with agents being extremely annoyed about the extra time required and ranting about how terrible the consequences would be if everybody did so. Such passengers sometimes lose property beyond prohibited items, and are powerless to do anything about it.
If the passenger tries to complain after, the TSA can simply deny the truth and claim it doesn't happen, or claim the passenger was doing something wrong. The passenger may not have any access to TSA video records which would disprove their claims, as that's considered secret, unless the records clearly show that the passenger was in fact in the wrong. Signs in security screening areas clearly prohibit recording, communicating the message that the passenger cannot have any recording evidence and their word is easily discounted compared to someone in uniform.
The elimination of ways in which officers can be held accountable opens the door to abuse of power (regardless of whether or not agents legally have much power) and leads to more situations in which the accountability is desired/necessary.
What does the law actually say regarding passengers' rights (or prohibitions) on recording interactions with TSA officers? What punishments are they allowed to institute on a passenger who attempts to record, beyond seizure of the passenger's property and detention past the passenger's flight departure time?