Users flagged it and a mod applied two kinds of standard penalty to it: one because it was a copycat post that added no information to the two major articles/threads already on the front page, and two because it was an unsubstantive rant.

Those penalties are standard because follow-up posts (e.g. that try to capitalize on hot stories to get cheap attention) and informationless rants routinely get tons of upvotes—many more than the substantive stories that HN is supposed to be for. That's a well-known weakness of the upvoting system. HN can't live by upvotes alone. If we didn't have countervailing mechanisms such as moderation, the site would not survive. I've written about this lots of times, e.g. https://news.ycombinator.com/item?id=10292239.

It had nothing to do with San Francisco (the moderator was elsewhere), nor with the rant being about Silicon Valley, etc.; anyone familiar with HN knows that critiques of all those things appear here all the time, and that's fine. We're hoping for thoughtful critique, though, not rage trolling.