People continue to report sites like that for the hate speech, racism and so on, and Disqus doesn't do anything. They could easily drop the entire site.

Their customer is the site, not the commentators (or people reporting negative comments)? So dropping an entire site due to a lot of complaints would just hurt their revenue. Also it wouldn't necessarily be fair to the site if there's a lot of trolls and racists etc in the comments through no fault of the site.