TV, magazines have to choose _one_ editorial line at a given time. Social media can present everyone their own bubble, and so it has bad side effects. When you have a forum, everyone is presented the same content. For example, this results in administrators being aware of bad content most of the time (at least in the few forums I follow). Everyone on HN see the same ranking. Social media and recommendation engines though, will send you into your own rabbit hole of a handful of interests. I advise you to view the documentary, this will answer your question best.