Over the years I've come across a few online communities that have noticeably higher conversation quality than the rest of the internet. The one thing all of those places had in common is a very strict moderation policy.

Not every forum/community/website should tolerate literally all people. It's never helpful to engage with trolls and if people aren't willing to argue in good faith than they need to go. I've seen tons of communities slowly lose their identity because they were too accepting of counterproductive conversations and bad faith arguments.

The idea of this form of tolerance comes from the goal be open minded and listen to opposite arguments, as well as to prevent a community from turning into an echo-chamber (or a cult), but I think it's better to lean towards heavy moderation. Banning someone who would be a good fit for the community is unfortunate, but ultimately not a huge loss. Not banning even one troll can drag down a whole community.