Get angry at the people that make policy, not the people that enforce it.
Sure, the IRS could be nicer. However, as someone who had to handle a policy enforcement role from time to time...I know the people I had to enforce policy on hate me, personally. However, I'm just enforcing policy. That enforcement is basically an email saying "No, disregard what X told you because Y is current policy."
People at the bottom usually aren't assholes "just because". We become assholes because people get angry with us over stuff we have no control over [unless we quit].
If you don't fix the policies, they just hire replacements. You even admit it is how it works.
"The strategy seems to make a lot of TSA employees feel bad, so the turnover there is quite high, but enough people need any job just to make ends meet that the overall effect to their workforce isn't very much."
You also didn't think about the logical result of pushing out the people who would feel bad about bad policies. It means you leave only the desperate & the bad people running the organization. Well done! You've removed everyone with a hint of moral fiber and/or soul from the enforcement role. And then you'll be surprised when no decent person is there to help you when there is an issue.
Ever heard of "Good cop, bad cop" ?