You can do that by mass censorship. We already have massive squads of minimum wage people combing through every post on the web in order to delete things, so just pull that into a regulatory agency instead of letting social networks regulate themselves. We could call it the Department of Truth. If you want to scrub the internet, it's actually pretty easy. Put literal cops on every message board, make every board record ips and block VPNs, watch every tor node, root every phone.

The only hard part is getting a majority of people to think that's a good idea, or at least to stay silent about it. If you look at history, though, it's actually not so hard. It'll probably happen eventually, although depending on your belief system, you might be upset at the administration that ends up with those abilities.

This isn't about that, it's about allowing more room for competitors in the market. If there's any relation, it would be that facebook wouldn't be able to by itself dictate acceptable speech (against its will, of course; if facebook had its way, it would only censor posts about facebook.)