I got banned from a subreddit because the mod had this "not with us, you are against us"argument. It was years ago, but IIRC I was posting against a comment calling for assaulting men to balance out the abuse of women.
To be honest, I think I may have seen more banning on Lemmy though. I've noticed a few cases where the admins have banned people with objectionable opinions. In all fairness, these were the type people you would avoid at parties, but it does give me pause. In reddit if you get banned from a particular subreddit you still keep your identity and participate in other subreddits. In Lemmy, you are at the mercy of your server, and if a large server bans you, it would essentially remove you from all of their communities that otherwise might accept you. I worry that this is creating an echo chamber.