Thought experiment. Suppose there was a planet, and on this planet, there is a population which is 90% left-handed and 10% right-handed. Left-handed people on this planet are intensely uncomfortable and disinterested in having anything to say, do, or hear with right-handers, and on public forums, where they have equal votes, they systematically silence, erase, and downvote any comments that even so much as hint at the existence of left-handed people. When this is pointed out, someone shrugs, and says, well, I guess people are not that interested in right-handed people.

Meanwhile, every other article, for months at a stretch, is vile slander about a supposed surge in right-handedness.

I claim that would still be an unjust state of affairs, and would still be broken moderation, even if a majority of people on this fictitious planet's Internet were happy with the arrangement.

Minority rights are a thing, you understand? There is such a thing as a tyranny of the majority. It is solely addressable through enlightened moderation that seeks to protect minority voices.

That's why "The hard part is convincing others what you want to say is what they want to see here." It's not that they need to read everything, it's that they need to see those things they typically want to ignore as something worth them spending time on. No amount of moderation will make people spend time reading things they aren't interested in reading. Part of this is you end up with communities with different focus, and that's usually the way these kinds of differences co-exist in the same world at scale. Once the communities get large enough, they are in some way forced to find neutral ways to interact. Typically this happens more in the real world than on the internet.

The only time this really breaks is when the divider isn't related to content, rather some arbitrary attribute unrelated to it. E.g. if a conversation about the best quality paints ignores someone because of their handedness. The content of what they were saying had nothing to do with the exclusion so people want to protect against those kind of exclusions. The same feeling does not extend to those that want to bring a content reason for exclusion into the conversation, e.g. someone that constantly talks about how paint is a conspiracy by $BigCorp and can't talk about paint without always bringing it up. In that case the person needs to find people interested in talking about $BigCorp paint conspiracies, not a moderator to force people to listen to them.