So /r/politics is much better because instead of taking down "alternative opinions" they just downvote it? I am not convinced. Effectively downvoting alternative opinions not only effectively makes them completely hidden from view for most users (under a "this comment has too many downvotes" barrier), but the users who do stumble upon those massively downvoted "alternative opinion" comments will get a nice dopamine rush from seeing their own opinions further re-enforced because the downvotes must mean this opinion is wrong.
Both are insidious and both behaviors massively contribute to group think bubbles. I don't think the pattern of behavior of one is massively better and more healthy than the other.
Better than moderators doing it. Post something that deviates from what the moderators of r/conservative consider acceptable conservatism and they just ban you. If the community legitimately downvotes you, then at least you're facing garden variety groupthink instead of "my way or the highway" of a couple mods enforcing what is acceptable discussion.
This is a pattern. Trump, at his coyly named "Truth Social" bans more people than Twitter ever did. And not for violent threats, either, but for simply disagreeing with his narrative.
Perhaps 80% of r/conservative threads can only be commented on by flaired users. Certainly all the threads one would actually want to contribute to at any rate. How do you get a flair? You have to post conservative-sounding things elsewhere or in the non-flair-only threads. Only once you've established that you're not going to deviate from the groupthink will you be allowed to participate in the community.
Conversely, r/politics is a free-for-all. Granted, there is clear downvote brigading on alternative opinions but they do not get taken down ever. HN is going to read your "intentionally one-sided" quip and not understand how correct you truly are.