> I believe there really are undesirables -- people who have demonstrated an inability to participate in civil society and who eventually drive away or drown out all other perspectives in a community.
and
> Sure there are undesirables in the world wide web: neo-nazies, Q-anon, pedos & NAMBLA, Russian propaganda, spammers and carders etc.
Where pre listing categories and ideas that are explicitly wrongthink, versus people able to participate in a community following guidelines and an etiquette. It's not at all funny or surprising, that each community that adopts the latter, find the list growing until it's a niche community by exclusion.
The idea that any meeting place that says it's for "free thinking" or "all ideas" is a mistake. Most communities want to stick to some niche topic and use the "open" phrasing to try to grow any participation at all.