Tell me then how open and good the discussion is on 8chan or the other uncensored free speech sites like it. Any site that tries to make their site have unequivocal free speech has always led to being a site full of trolls, nazis, and edgy teens. This isn’t conductive for quality discussion. (unless you want “quality discussion” of race science and other fascist garbage) If you want good discussion then you need to moderate the space. Go to any technology board and see how much they moderate. Go to hobby forums and see how much they moderate. Some may be more lax than others, but moderation is key to making your site a place where people enjoy being and feel comfortable enough to participate.
The reason lemmy has a hardcoded slur filter is because almost all the reddit alternatives end up as alt-right cesspools. The hardcoded slur filter is to make it less appealing to those people… It does cause some issues in other languages and the lemmy devs know and are working on fixing that.