You're listing several examples, including /r/conservative, yet even though this subreddit is widely known (on Reddit) to be a censored echo-chamber, you do not mention this aspect. I find it hard to believe, that this would be a coincidence.
That's a very weak argument in my opinion.
How does the moderation in /r/conservatives, a subreddit for conservatives to discuss "from a distinctly conservative point of view", concern a liberal like yourself in any way?
This isn't a subreddit you need to participate in. I think it's more relevant how default subreddits or country subreddits are moderated in a similar way.
From the HN guidelines:
> Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith
Let's aim to keep HN better and more pleasant to use than Reddit;)