That's not an accurate description. I think you might be falling prey to the sample bias where people heavily weight the comments they dislike and don't so much notice the others [1]. In fact that 3-comment thread covered the spectrum: enthusiasm, skepticism, bewilderment. I'd say it set the stage nicely for the next 12 years.
Of the 20 most recent comments, I'd say 12 are negative, 4 are positive and 4 are neutral. (Your comment showed up in my search and I counted it as neutral.)
Oh yes, but that's a much different question and is strongly conditioned by where Bitcoin and cryptocurrency are in the hype cycle (I'm using that term empirically, not normatively). You'll find at least that much negativity about other technologies and startups that have gotten to similar stages of (let's call it) ultrasuccess. Just look at the threads on Airbnb or Uber, for example. They're so vitriolic and repetitive that thoughtful discussion is almost impossible. We can speculate about the reasons for this but it definitely doesn't have to do with sentiment against new tech; it's a later-stage phenomenon.
'Ethical concerns' only covers a subset of these cases and the phenomenon is noticeably similar across the entire set, so I don't think ethics is a convincing explanation.
People reach for the handiest hammer, but it doesn't follow that the hammer is driving the hammering. Ethical concerns are the best hammer, of course, because then one's own motives are unimpeachable; but failing that, you'll see comments about the business being shitty for other reasons—"it used to be good but they've been declining for years and I can't even use it anymore" is one, and "how is this a viable business, look at those financials, doesn't anybody care about profit anymore god this world is insane" is another.
I don't believe Dropbox threads are generally friendly to Dropbox anymore, and I'm pretty sure Digital Ocean has been on the rack here too. Today's thread was a noticeable exception. Most S-1 threads are pretty cranky in general.
The original description may not be correct, but HN is almost certainly iconoclastic, and ever since cyrptocurrencies became mainstream HN has responded in kind by attacking them.
Source: Day 1 HN post -> https://news.ycombinator.com/item?id=599852
If you have a truly revolutionary idea, expect the conventional wisdom on this website to be extremely negative.