[somenameforme]

I don't think its individual 'truth failures' driving such a largescale change, but rather a gradual big-picture slide. For a softball example, an article on the front page of Hacker News right now is "Study Suggests Fructose Could Drive Alzheimer's Disease." See enough articles making such declarations and where they lead, and you gradually start dismissing them as probable junk without even opening them. It's not because you've carefully debunked past studies, but simply because what was implied (major breakthrough) and what happened (nothing) don't jive.

So a better example for your search might be to go back to the Internet Archive, and grab the NYTimes from a year ago. And start reading the articles, and see if things ended up logically leading where the articles imply they would. Beyond this I also don't think you can, in good faith, disentangle opinion from fact. Yes we SHOULD, but it's not like people carefully scrutinize a headline or article to assess whether it was categorized as opinion, and then largely disregard it if so. People treat opinion and factual reporting, more or less, the same. And sites intentionally interweave them in order to drive clicks. So you can't have your cake and eat it. Generate clicks by publishing junk, and people are just going to remember you publishing junk.