You're missing what I think is one of the primary points he's trying to make - answering any of those questions instantly puts him at risk of lying to a federal officer, which is a criminal act.
In order to be polite, you have to risk being a criminal. Ergo, it makes more sense to be a little rude (and being silent isn't that rude, _particularly_ to a federal officer - for them being silent is simply one of a series of acceptable responses) and forgo the risk of criminal charges. Are you being a douchebag to a police officer when you refuse consent to a search?
He also lists a number of countries in which Customs and Immigration believe their job is "Customs and Immigration" and _not_ getting historical biographical information.
There really is a fundamental privacy issue.
True Story:
I was crossing the border from Canada into the United States in 2003, and was with a friend (an attractive blonde, Canadian, that I had declared our relationship to be "friend") at a ground crossing (Peace Arch, in BC) - we were pulled over for secondary, and went into the Immigration office. They asked us a number of questions, all of which I answered to be the best of my ability (I have neither the courage, nor moral fiber of the author - wish I did) - and they were preparing to let us go. Just as we were packing up our passports, and leaving, the Immigration Officer pulled a "Columbo" and said, "Oh, one more thing - are you still dating that Red Head, Marjorie?" I was a little floored - I had crossed the border _once_ with a (red headed) girlfriend in 1999 - that information (that we were dating, the color of her hair, her name) was clearly in a federal file on me, and they were using it to get a reaction from my companion (who, thank goodness, was actually a friend as I had described her).
So, from a privacy perspective, just be aware that as you answer all of these questions, they are going into a federal database, that certainly can paint quite a detailed pictured of your life. If you are willing to remain silent, then they have less to enter into their database.
It's interesting how when people buck the status-quo, even just a little bit, they get tagged with the "douchebag" title. God bless them.
EDIT: As a follow-on, I should note that as a Canadian, I really have no excuse not to answer all questions asked by American Customs and Immigration, but, very ironically, as a TN Computer Systems Analyst, I am almost _never_ asked any questions _whatsoever_ by American C&I, and the rare time they ask me anything, it is always the single (very reasonable) "Who are you working for". Returning to Canada, on the other hand, is an exercise in what did I do in the US, where I'll be going, what I'll be doing, who I'll be staying with, for how long, etc, etc...