This is something I think Facebook has been unfairly attacked for. Yes, Facebook didn't do everything perfectly, sometimes they were negligent, but they did also try quite a bit (both financially and manpower-wise).
The reality is, anyone else would've failed the same way. The problem wasn't that Facebook was evil or negligent, it was that being the "primary communications platform for all of humanity" was always going to be impossible to moderate, and it was always going to turn nasty.