The "if you accept the premises" is, well, one hell of a big "if".
Cory seems to believe that companies are not in the business of making money, but rather are in the business of controlling peoples' lives as totally as possible, and proceeds from there. The mismatch of this belief with actual reality, and the resulting conclusions drawn with respect to, e.g., vast multinational conspiracies attempting to micromanage individual people, is of a sort which, given any other target, would result in institutionalization for paranoid psychosis.
Not at all. I don't think Apple wants closed systems for their own sake, but I do think they believe that closed systems will be more profitable for them. The end result is the same.
Apple and others are trying to create a future where closed systems are the default, and open systems are either illegal or heavily marginalized.
This does not express the opinion that Apple believes they can make more money from selling closed systems. This expresses the opinion that Apple's goal is not to make money but rather to impose control on people for... well, I'm not honestly sure what reason.
And that sort of implication is everywhere in discussion on places like HN, despite the fact that it literally goes off the deep end into unfounded paranoia; "Steve Jobs wants to keep me from using Google Voice" is taken not as a statement about how he'd prefer to have his company get your money, but as a statement about how he's an evil megalomanic obsessed with controlling peoples' lives. Which is really only a step away from (and logically about as sensible as) "he's working with the Bilderbergers and the lizard people to cover up the truth about JFK's role in 9/11".
I myself find it difficult to imagine a future where the vast majority of applications are not web apps hosted on private servers. If you take that to be the likely future, then what you can and can't run natively on your computer (with the exception of the browser) becomes irrelevant. Debating whether or not you have the freedom to run arbitrary native code will be like arguing over having the freedom to install your own BIOS.
I'd guess Cory's complaint is not specifically that iPads are closed, but that Apple and others are trying to create a future where closed systems are the default, and open systems are either illegal or heavily marginalized. If you accept the premises, that actually is a big deal.
one guy, forcefully advocating an opinion about something that really doesn't matter that much to most people, and that he can't really change.
So, pretty much like nearly any public advocacy of anything.