>I've hardly ever seen serious insults on Facebook

Every once in a while curiosity and boredom get the better of me and I visit ESPN or some other mainstream news site that uses FB profiles for the comments section and I almost always walk away shocked at the kind of comments people are willing to post while directly linking to their real name and profile, often containing their place of employment. Respectfully, if you haven't seen serious insults on FB, or at least on sites using FB profile logins, you haven't been looking hard enough.