It depends on which organization they're in. Plenty of them think of their job as legal PR, finding the loosest precedent they can to justify the organizations actions as accepted and legal.
I've never understood why departments are reporting to themselves and not an independent inspector.
Granted, politicians and the people they appoint will do anything to justify their actions, even across organizations, but it might open the door for political opponents to call each other out, on their bad actions.
Contact your federal senators and/or federal house reps, and tell them that USPS is sending pictures of other peoples' mail.
Or if you dont want to do that, then contact USPS Office of Inspector General. uspsoig.gov/
The IG's are absolutely terrifying if you're on the wrong side. And you're 100% in the right, and they're in the wrong.