Yes, the anonymity (most) users enjoy on Reddit is interpreted by some as freedom to be assholes or trolls. Even then, especially in the more heavily moderated or off-the-beaten-path subreddits, you get some very high quality conversations. It's not uncommon to see threads of multi-paragraph comments going back and forth many comments deep. I think Facebook's lack of anonymity already goes a long way toward keeping things civil there, and what little shitposting does happen there would probably get downvoted and possibly hidden by default when below a certain threshold if FB had that capability.