It costs nothing to start a new subreddit if you want different rules. And if lots of Redditors agree with you, they’ll happily follow you.
Regardless, it's still frustrating. Especially when they cannot tell you which "rule" you broke, so they resort to telling you they can use their discretion to ban you for any reason (which is usually some sort of agenda that becomes apparent after you've tried to have a civil discussion about why you were banned). It's what drove me away from that platform, and I'm sure I'm not the only one, so I guess not telling users also prevents future issues, in a way.
Sometimes you just have to show boorish guests the door.
Let it run on a set of rules, and count votes to change rules. Now you have DemocracyBot
(Just like every other group: self-serving.)
One of the weaknesses of this is how, at least on some subs, mods are able to censor discussion largely unnoticed, without being held accountable to the community. See r/declineintocensorship, r/watchredditdie, and r/yallcantbehave for several examples of egotistical mods overextending their role with no real benefit to the community.
I can't help but think that there's a way to hold mods more accountable to their communities. For example, if the modded comment wasn't spam, it could say "this post was removed for breaking rule x which states y. Click here to see the comment," with the mod's username attached.
I would also like to see statistics on removed posts, where a subreddit gets some sort of penalty for censoring too much, such as not appearing on /r/all, or becoming downweighted in some way.
Which certainly doesn't violate any laws.
The unintended consequence, however, is more isolation and less engagement with ideas you don't already subscribe to or people you don't normally encounter.
This is not a Reddit specific problem of course, it applies to Twitter and Facebook or any other social media platform. But it's concerning and difficult to find any easy and obvious solutions.