That's an opinion, not demonstrated fact, and one I don't agree with.
Customs officials may be in some position of authority, but they are still people. People generally prefer to be treated with respect, politeness, and civility. Your every interaction with someone in authority is not an alpha-male/top-dog struggle for dominance.
Regardless of that, there's a difference between polite defiance and rude defiance, often a big one. Odds are you'll get a better response from the former, one that allows you to exercise your rights without coming off as a dick. At the very least it's easier to earn sympathy if you're still mistreated.
Customs officials may be in some position of authority, but they are still people. People generally prefer to be treated with respect, politeness, and civility. Your every interaction with someone in authority is not an alpha-male/top-dog struggle for dominance.
Regardless of that, there's a difference between polite defiance and rude defiance, often a big one. Odds are you'll get a better response from the former, one that allows you to exercise your rights without coming off as a dick. At the very least it's easier to earn sympathy if you're still mistreated.