It’s one thing to enable people to seek out extremist communities on their own. It’s quite another to build recommendation systems that push people towards these communities. That’s putting a thumb on the scale and that’s entirely Facebook’s doing.

This is one example, and it’s quite possibly a poor example as it is a partisan example, but Reddit allows The_Donald subreddit to remain open, but it has been delisted from search, the front page, and Reddit’s recommendation systems.