FWIW, as a total aside, this is a f***ing disgusting book! If you look at the “scientific” references relating to any of these studies, they all suffer from horrendous scientific and analytical errors, which render them useless. As you point out, they were alone, enough to discredit all the studies and inferences from those studies.
So we have ourselves a position of scientific incompetence, coupled with a willingness to act to discriminate against particular demographics on any pseudo-legitimate grounds (alternative-legitimacy?).
The last time this happened was in the late 1930’s off the back of the pseudo-science of the eugenics movement. It led to “extermination” of 6 million people and a war which totaled 20 million dead. People who may choose to poo-poo that sentence because they see it as levying an accusation, forget that is the truth, regardless of any accusation they perceive.
The problem Facebook has is that it is a social network. It’s whole reason for its existence is to connect people and it can’t do it without having right-wing folk in there too. So oddly, I get where they are coming from on ideological diversity.
What it doesn’t have to do though, is allow hate to spread. If they want to be representative of the human race, they have to be representative of it’s tendency for policing and governance, or give more power to individuals over the ability to call out abuses. Facebook is a platform that has actively rejected calls for the removal of abhorrent, offensive material and has been guilty of not taking abuses, such as racism and cyber-bullying seriously. They were also implicated in the spreading of “fake news” during the Trump campaign (they didn’t carry it out, they were simply the vehicle for it to spread through the actions of organisations like Cambridge Analytica and SLC Group). Such things spread memetically, like viruses. There is no antidote when the whole organism is infected.
Finding the sweet spot is also a very different beast. Alternative facters are not prone to truth, logic or science, which ironically makes them sitting ducks for companies such as Cambridge Analytica. Hence, using our ability with reason, is useless and is akin to discussions about the [non]existence of god, in a grudge match between real science and the BS science of the door-to-door.