The idea that a social networking site has caused people to be more insular and less connected with each other and is therefore responsible for the existence a hate group is flatly laughable. Social networking, including and especially Facebook has had exactly the opposite effect. It has exponentially increased the exchange of information among parties who otherwise wouldn't communicate.
Just because you can also use it to exchange information that you'd rather not see exchanged doesn't mean that the tool itself is at fault.
This isn't what people are talking about, nor is it the problem here.
First off, Facebook might be (should be) in legal trouble because they sold ad space to a foreign entity for political advertising. That's against the law.
Also, it could be argued that since relying less of human curation and more on algorithms, increasing the exchange of information is exactly what Facebook DOESN'T do. Determining the political leaning of its users and then force-feeding them only content that aligns with that, combined with the unchecked flooding of unvetted content sources, is precisely what we dealt with last year, with conservatives being flooded with ridiculous stories about Hillary Clinton running a pedophilia ring through a pizza parlor that, surprise surprise, largely originated from Russian and Macedonian troll farms.
Facilitating the exchange of information and making sure that exchange isn't abused SHOULD go hand-in-hand. Facebook completely abdicated their responsibility here, and potentially broke the law in the process. They should absolutely be taken to task for it.