It depends on what percentage of content submitters get pissed off enough to move on to another website. Since the vast majority of reddit users don't even have an account, if a significant number of active users leave, then the overall content decreases, which can impact all of these more numerous users. I can only assume that reddit has performed some sort of analysis to determine the overall impact, and that they feel that the negative impact of undoing their free speech policies is less than the positives of banning hateful subreddits. We'll see.