The concept is valuable because it identifies a predator species that kills the intellectual curiosity HN exists for. This is independent of the content of the rant. If an army tramples your garden, it doesn't matter whether they led with their left feet or right, or what color the uniforms were.
You're thinking about this in terms of specific comments and political views, while for us it is a systemic problem of how to run a large, anonymous internet forum that doesn't self-destruct. These are two different perspectives. That gap is why people make the mistake of feeling certain that we're secretly biased in favor of $X, where $X has nothing to do with us but is rather the inversion of their own ideological side. All sides think this, leading to many contradictory-yet-somehow-all-the-same charges of manipulation. I presume it is the same cognitive bias that makes sports fans 'know' that the refs are secretly against their team.
Often people throw in seemingly factual statements like you did here: "because they agree with the increasingly rather odd Silicon Valley...". A statement like that is simply invented. You don't know it; you can't know it; nor can you point to any statement showing it. It just feels like it's true. Meanwhile opposite people say opposite things, feeling just the same way that you do. https://news.ycombinator.com/item?id=16098840 is typical.
There's an incongruence between saying that HN is filled with quality discussion ("hardly any genuine spam or trolling") and that the mods are biased censors (Soviet-style! adds your sibling commenter) stamping out good discussion. That would hardly be quality-enhancing behavior. The assumption that if only we would stop doing what we do, HN would get better, is magical thinking. If HN is any good, how did it get good to begin with? How could it stay any good, if the moderators are so repellent?
Re dead comments, there are lots of reasons why that happens. Sometimes it's software that we've written based on past patterns of abuse; sometimes it's user flags, etc. These methods are indispensable but imperfect, which is why we created the 'vouch' feature for community members to rescue dead comments that shouldn't be dead. Anyone with karma > 30 can click a comment's timestamp to go to its page, then click 'vouch'. This way, instead of interpreting it as censorship and complaining about the refs, you and your fellow community members can simply reverse it. How Soviet is that!