What I am going to do is point out that hey, maybe there are people out there that troll just to troll or troll for a particular cause, and there's a lot of them. When you have a few different sides that are generally isolated from each other and already struggling to have a conversation and throw trolls and paid trolls (astroturfing) onto the same platform, you don't have a platform that is conducive to these various sides having any kind of conversation because there are groups of people that are actively working to prevent this. It doesn't even take a very strong push to keep them apart either, they were already inclined to isolate themselves in meatspace, why would cyberspace be any different?
Facebook has more than a quarter of the Earth's population on their platform. Undoubtedly this is a hard problem to solve. An authoritarian approach is probably what they are going to end up having to go with because they're not a country or a religion, they're a bloody online advertising company.