Further for your info: Hacker News does not "need a filter lest you quote a sentence from some movie", it only needs to take responsibility of you commit copyright infringement by doing so.
I’d happily let Hacker News go if it means other such platforms go with it.
I'll take as a given that many platforms are profiting from copyrighted content uploaded by users, but I very much doubt that the copyright owners would secure any of those profits for themselves if the platforms in question were driven out of existence.
Do you believe otherwise? If so, why?
CENTURION: Has what, sir?
CENTURION: Yes. He did, sir.
PILATE: No, no. Spiwit, siw. Um, bwavado. A touch of dewwing-do.
CENTURION: Oh. Ahh, about eleven, sir.
PILATE: So, you dare to waid us.
BRIAN: To what, sir?
PILATE: Stwike him, Centuwion, vewy woughly!
The movie studio could now hold HN liable.
Well, except that HN is not under EU jurisdiction, so it could probably choose to ignore EU court decisions against it. Bigger platforms of course won't have that luxury, so they'd need to come up with some way of limiting or avoiding that liability... or maybe just blocking EU users.
He's using the quote to make an unrelated point. This wouldn't be considered copyright infringement anywhere you have an impartial judiciary.