It seems pretty clear that Harry's opposition to Azkaban is because of the Dementors. He isn't opposed to prisons in general, and all of his emotive thinking about Azkaban has centered on the Dementors.
And we've established that the Dementors are, in the HP:MORverse, instances of Death. I'll admit that I haven't the foggiest clue what that actually means, but that's kind of true of pretty much all magic; I accept it on narrative grounds.
So I stand by the original statement.
Harry is opposed to people feeding other people to Dementors, slowly, over many years, until they die. If Dementors were just dangerous evil creatures roaming out there and occasionally killing unlucky people who didn't Apparate away in time - like trolls, or dragons - Harry wouldn't care much about them and their association with Death.
This is precisely what I'm saying: he previously swore to end death (not just Dementors!) but now he's swearing to end Azkaban - a much smaller goal. In fact it's insignificant in comparison. Let's hope it doesn't get exclusive priority on Harry's time.
Update: Discussion has moved on to a new thread.
After 61 chapters of Harry Potter and the Methods of Rationality and 5 discussion threads with over 500 comments each, HPMOR discussion has graduated from the main page and moved into the Less Wrong discussion section (which seems like a more appropriate location). You can post all of your insights, speculation, and, well, discussion about Eliezer Yudkowsky's Harry Potter fanfic here.
Previous threads are available under the harry_potter tag on the main page (or: one, two, three, four, five); this and future threads will be found under the discussion section tag (since there is a separate tag system for the discussion section). See also the author page for (almost) all things HPMOR, and AdeleneDawner's Author's Notes archive for one thing that the author page is missing.
As a reminder, it's useful to indicate at the start of your comment which chapter you are commenting on. Time passes but your comment stays the same.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: