I think the biggest concern is when platforms start to police illegal speech, and countries make political dissent illegal.
But now that reddit has become something of a cultural focal point on the internet, it's started to draw attention from the media at large and suddenly the operators felt a little embarrassed that they had to defend subreddits such as /r/fatpeoplehate, /r/jailbat, /r/niggers etc. So I imagine they just said "fuck it, it's more trouble than it's worth", and despite a month or two of banhammer-whack-a-mole with fuck-stupid-dictator-sjw-cunt-ellen-mao subreddits, the site continued to flourish, and all the free-speech purists finally woke up to the startling truth that reddit.com was really just an internet startup and not a platform to empower the oppressed masses...
Until they banned another subreddit.