Are you joking? There's a huge number of cesspools still on reddit. Stuff like thedonald, theredpill, all sorts of blatantly racist/misogynistic communities.
Also, quarantined != banned. It's still on reddit, and those users spread out onto other non-quarantined subreddits and spew the same kind of garbage.
Ban the cesspools and most of those people will actually leave the site for good, as what drew them to it in the first place is now gone. You also no longer have any cesspools serving as negative guideposts for making bad contributions. So if you moderate your site well, and just get rid of this kind of stuff, it ends up much better in the long run.
So now it's the truest propaganda machine, you're saying. Approved users only for consumption by a dedicated subscriber base.
Edit: Also the sidebar says there are 600 active users. I assume that includes me following your link. For comparison /r/news has ~68,000 users as of this writing.