"Why was there a part of him that seemed to get angry at the old wizard beyond reason...

Because that's what taboo tradeoffs are all about. You feel a sacred value that cannot be traded for a mundane one. The human response to a threat to a sacred value is anger. Also, at least in Harry's case, the anger seems to be a defense mechanism of the sacred values against reason. Get pissed off as a means of mental evasion. The part that defends the sacred values will lie, refuse to think, and refuse to see reality. Also, there's some resentment at Dumbledore at making him see his own inconsistency and self duplicity.

It is interesting. EY is treading perilously close to politics here. As I think about politics, almost all idiocy centers on various Taboo Tradeoffs, where some sacred value is at odds with a seemingly mundane one, and the idiocy floweth.

The sacred values that worked in small bands on the savannah don't scale to people in societies of hundreds of millions trying to make collective decisions. What are people to do? Is it true that humans can't live any other way?

I'm interested in seeing what he has to say on this.

I don't think it has anything to do with magic and horcruxes. It's a human problem. That's why it's interesting.