The admins didn't want to ban /r/TheFappening but decided to after they got a flood of DMCA takedowns from the celebs lawyers. The sub actually broke the site because of how much traffic it was generating and that was almost 5 days before it got banned. They knew about the sub for several days and let it go because they have a hands-off policy and don't generally step in unless something drastic happens.
> Although, as of recently the reddit administrators started banning some of the more racist subreddits
Not completely sure, but IIRC those weren't banned because of racism but brigading/doxing. Which of course is bound to happen with subreddits catering to extremists.
Although, as of recently the reddit administrators started banning some of the more racist subreddits even though they didn't have any official change in policy.