The article itself was a bit disappointing because it focused on political issues. In my opinion the strength of HN in this regard is that it is both a "sjw cesspool" and a "haven for alt-right", as evidenced by the fact that a comment on a controversial topic can easily float near zero points while raking in both upvotes and downvotes. And even those who refer to it as "the orange site" still come back and comment. In other words, HN may be an echo chamber but it is a pretty big one with a lot of voices in it.
Looked it up, it means "social justice warrior", defined by Wikipedia as "a pejorative term for an individual who promotes socially progressive views, including feminism, civil rights, and multiculturalism, as well as identity politics".