According to the official Reddit rules, the offending user is supposed to be banned, but there is no requirement saying the post must be removed. Removing a political post that only gets a call to brigade to a \~500 person channel *after* the post reaches the front page could be a politically motivated take-down, not necessarily by the mod themselves but by a misleading reporter. Say for example I want to take down a Bernie post that reaches the front page of Reddit, all I have to do is post it on another sub / social media or get someone else to do it, ask for upvotes, and then report it so the post gets taken down. That's why you're supposed to ban the user or only delete new posts, not old posts already on the front page.