Disagree.
While there is something to be said about the preponderance of evidence, you cannot in the same breath point out the rise of fringe conspiracy theories while also point to majority opinion holding sway.
Prior to social media we had mass media, whispering campaigns, and gossip galore. Same problems and eventually people get wise to who is lying to them and excise them from their attention, especially with mass repetition (see cable tv).
Truth of the matter is the quality of discourse has plummeted (especially from the early days of the web) with attention whores to monetary gains and censorship and gamification. The signal to noise ratio isn't worth the effort, so even more people with wise observations check-out and leave the banal to dominate the discussion.
"Social media" is just a boogeyman, much like comic books, pinball, and telephones before. The problem isn't so much as described (Mcluhan would have something to say about that), but the gatekeepers tut-tutting the unvarnished public and the commercialization of the web.