Why are we having this conversation here rather than on Reddit or Twitter? For me it's because I prefer a moderated forum. We don't have pictures at all here (though you can link to them) which makes some issues non-problems.
Many people are more interested in avoiding spam and abuse than they are in seeing something outrageous. As long as you have forum-shopping the more highly moderated places have an advantage, at least some of the time.
Facebook is in the moderation business. They're going to screw up sometimes but they're not going to stop moderating. On the other side you often have people saying they're not doing enough about abuse.
Side note: Reddit has lots of heavily moderated subs of excellent quality. HN is perhaps a bit less focused than them. I don't see why r/hackernews couldn't be a thing.
Many people are more interested in avoiding spam and abuse than they are in seeing something outrageous. As long as you have forum-shopping the more highly moderated places have an advantage, at least some of the time.
Facebook is in the moderation business. They're going to screw up sometimes but they're not going to stop moderating. On the other side you often have people saying they're not doing enough about abuse.