In my opinion, Facebook is trying to maintain the illusion that this kind of content isn't being posted at all, that they present a "safe" environment for their

In my opinion, Facebook is trying to maintain the illusion that this kind of content isn't being posted at all, that they present a "safe" environment for their customers. If people started to see this kind of content, they might be motivated to stop using Facebook all together. It might also prevent de-friending; I strongly suspect that Facebook doesn't want people to "de-friend" each other. Note how many alternatives they provide to actually "de-friending" (i.e. the "snooze" option).