There are many factors at play. Each sub has it's own moderation team that can decide what content to allow or not allow on their subreddit. This can result in bans for any reason, at any time. I am banned from the_donald for "concern trolling" after questioning their pro-life arguments in cases of severe fetal abnormality. It doesn't fit what their great lord emperor Mike Pence says, so they can silence any dissent. It's their subreddit.

Also, some subreddits are not meant for debate or argument, they are meant for support. r/babybumps is for pregnant redditors and those who support them, per the subreddit description. They get anti-natalists or proponents of eugenics that want to come in and debate the ethics of birth with pregnant women, when it is not a debate subreddit, it is a support subreddit and not the place. Pregnant women don't go to r/childfree and argue why they should have children, that's a support subreddit for the decision to not have children. It is okay for groups to have a place free from having to constantly defend why they are in that group.