Can you explain how you managed to transit from "The banality of evil is probably the most important lesson" to "it's not obvious that the border police aren't thugs"? Are people thugs by default in your worldview? Or just all law enforcement officers?
People in positions of power often act inadvertently thuggish, yes. It's in the nature of positions of power and the human condition. It's why it's so important to have checks and balances, and ensure that those checks and balances are exercised regularly so that they don't get rusty from disuse.
Take the Nazis. It's not like every German was evil, or even that most Germans were evil. It was the situation and structure that was evil, and the social proof, and a hundred and one other things, that add up to decent people doing monstrous evil.
Character really doesn't matter for as much as a lot of people like to think. Almost everything people do comes down to their incentives and their situation, from the lowest thug to the most noble statesman. Ascribing flaws or nobility to character is a way of personalizing these situations, often to justify treating people with very few options with harshness and cruelty, while rewarding people in the position to do good with social standing and wealth, etc.
What the banality of evil suggests is that "evil" or in this case "thuggish" behavior is much more a function of social role, and less a function of character, than people thought. (Yes, it really was a radical idea -- recall that two-thirds of the people in Milgram's famous experiment went to shocking an unresponsive subject with 450 volts, when almost everyone had assumed, prior to the experiment actually being run, that only a one-in-a-thousand psychopath would get there. Check out Milgram's book Obedience To Authority for more details.)
You're doing a fine job illustrating the banality of evil, but you're not explaining what that has to do with the situation at hand. Yes, we need to be on guard for situations in which authoritarianism provides cover for evil. That's why we have a constitution and a court system and why we elect the people who create laws and appoint the people who enforce them.
