The existing practice is for the community of these sites to upvote good content and downvote bad content.
Separately, moderators purge controversial content as a check/balance to the voting system. If users feel that the moderation is inconsistent with their content desires, they choose a different site to frequent, as is the case in market systems.
Separately, moderators purge controversial content as a check/balance to the voting system. If users feel that the moderation is inconsistent with their content desires, they choose a different site to frequent, as is the case in market systems.