The main thing you seem to be missing though is that the subreddit is not meant to be a neutral ground for people to compare and discuss ideas.
It's a place to get concrete, consensus- and literature-based answers from people with real experience and practice at history. Having people in the comments presenting ahistorical information entirely outside of scholarly consensus only detracts from that goal.
So even if you consider this _only_ a power-vs-speech thing, there's still a strong argument that moderation is the correct step. When conversations detract from the stated purpose of the community they are restricted. Same as right here actually.
It's much, much cheaper for someone with outlandish views to shotgun you with questions than it is to answer them all in detail.
Combine this with the fact that there are fewer experts than there are trolls/people with outlandish views.
Further combine this with the fact that the trolls/outlandish views folks are not coming to get themselves educated, they are coming to try and convince others to hold their outlandish views.
How do you propose we keep a community resilient against that?
That said, it'd still lead to a degradation and constant mod cleanup work to post links to the FAQ and close the thread (if not closed, fellow travelers would upvote it and use it as a JAQ platform).
https://www.arkansasonline.com/news/2021/apr/08/house-advanc...
This is brought on by a change in the composition of the Supreme Court, and there's a significant chance it will permit creationism in schools. Expect to see more attempts to reach the Supreme Court to overturn its previous decisions, and if it does, expect a great many states to pass similar laws.
And then expand them.
Those with "outlandish" views, namely those who believe some people's lives are fundamentally worth less than others often turn this into a strategy. As long as Holocaust deniers are tolerated and especially counter-argued by everyone, Holocaust denial will be all that is being talked about because they take the stage.
Even if they lose the discussion, they win the topic of the day. And that topic gets gradually normalized into an acceptable position, pushing away others silently.
Arguing against outlandish views on merits is likely to be much more effective. Silencing opponents is using "might is right" approach -- just the type of logic that allowed many atrocities in the first place. My 2c.