Personally I don't think Facebook should censor anything except spam and posts that break the law like direct threats of violence and child abuse. However, I do think they have a responsibility when it comes to paid content and the algorithms they use to push content on people. Its one thing to have an uncensored forum where people might be exposed to things they seek out, and entirely another thing for Facebook to choose and collate what people are seeing. Once they do that, they share responsibility for the content people see, rather than just being a platform.