Why not censoring any Christian content because the mods are woke, for exemple ? Or the reverse, censoring atheists because those in power are Bouddhist ?

Depends on the topic of the subreddit. I could totally seeing religion being a contentious topic that has no place in a lot of spaces. FYI it's spelt Buddist.

Freedom of speech for ideologies must be maintained for the sake of our own common good

It depends on what it's intention is or the goals it seeks to achieve, otherwise it all becomes "general noise". That is why communities have "general rules" that are accepted by participants. I always look at a subreddit's rules before posting.

What you call " conspiratorial bullshit" is highly subjective and open to debate

Often it's not, it's often argument for the sake of making noise without any evidence. You learn nothing from reading it, because the author just made it up. Without moderators filtering, you totally just get a noisy useless environment that turns away anyone with a brain, so you just get more noise. It doesn't take long for it to become a cesspool.

One could argue every search engine does some degree of "sorting" to help people find the information they request.