Making it opt-out instead of opt-in is shitty. Here's a better idea: don't disrespect the hackernews users in the first place.
I mean no disrespect. The site simply wouldn't work without it. HN has a million users or so.
Opt out is the best compromise I can offer. Without it, no site is possible.
How is archiving content disrespectful toward the creators of the content? Are you also going to sue the Internet Archive?