All very good points, and convincingly presented. But I don't think anybody (nobody here, at least) is contesting that politeness is important and useful in social interactions.
The question was whether being polite or brusque (and he wasn't rude after all, just perfunctory and not actively polite) in refusing to answer CBP officers' questions would have made much of a difference to the CBP response.
If you cannot see that interacting with CBP officers is "social interaction", then I don't see where we can ever come to any agreement. And if you were not there and if there is also no videotape of the interaction, I don't see how you can assert with any certainty that he was not being rude at all. As I stated above, the vast majority of such things is conveyed not by words but by voice tone, body language, facial expression and so on. As far as I know, the only account of the incident is from his point of view. Perhaps the CBP officers have gotten together and written their own account, but so far I have seen no mention of it (and I consider that unlikely as it could potentially cost them their jobs -- security jobs typically require you to generally keep your mouth shut). His writing tone and his framing of things (that these people are "thugs" who deserve to be treated a certain way by him for, apparently, not simply up and quitting their jobs as proof that they don't agree with ...whatever he is taking issue with) doesn't give me much confidence that he wasn't rude in some way.
For that matter: Most people cannot up and quit their jobs. Having a job is not strong evidence that someone wholeheartedly supports and believes in all policies and practices of their place of employment. In many cases, it is only evidence that they prefer putting up with the crap at work to putting up with the alternatives (such as homelessness). Even in cases where someone does strongly disagree with what goes on at work, most people cannot afford to simply up and quit and there may be little they can do to change it while they are there. If they really feel strongly about it, they typically begin job hunting and leave as soon as is practicable without cutting their own throats. Additionally, if they have any sense, afterwards they tend to keep their mouths shut about the things they did not approve of. Talking trash about a former employer can be a good way to ensure that other people will be reluctant to hire you.
He makes snide remarks about the "low pay" of these people in a way which strikes me as classist and then makes even uglier remarks about how they deserve his treatment for not up and quitting which he claims they can do "at any time". He damns them coming and going, which does nothing to convince me he was even civil. Everything he wrote paints a picture of an individual with a chip on their shoulder who is actively looking to create such a confrontation. In his own words: "But that’s a small price to pay to remind these thugs that their powers are limited and restricted." So his stated goal was not to simply exercise his rights. His stated goal was to "teach them a lesson", in essence. That kind of goal is generally rife with unstated hostility.