[rchaud]

It only becomes a cesspool once it grows beyond the size where it can be moderated by users themselves. For example, I post on a soccer forum dedicated to a specific team. It's been around since 2000 or so, built using PHP forum software.

There is a shared culture between the users. While there are thousands of accounts, there are only a few hundred active users, so everyone 'knows' each to an extent. That's why when someone tells someone else that they're behaving badly, it's usually made in good faith. That creates a completely different feedback loop than on social media, where no one knows each other and their default position is to get defensive when called out about something.

These old-school forums still have admins, moderators and allow you to flag things like spam, hate speech etc, but they're rarely used, because when someone signs up for an account, you can assume that they're there to partake in the aforementioned shared culture.