Donald J. Trump and Hillary Clinton said this week that we should think about shutting down parts of the Internet to stop terrorist groups from inspiring and recruiting followers in distant lands. Mr. Trump even suggested an expert who’d be perfect for the job: “We have to go see Bill Gates and a lot of different people that really understand what’s happening, and we have to talk to them — maybe, in certain areas, closing that Internet up in some way,” he said on Monday in South Carolina.

Many online responded to Mr. Trump and Mrs. Clinton with jeers, pointing out both constitutional and technical limits to their plans. Mr. Gates, the Microsoft co-founder who now spends much of his time on philanthropy, has as much power to close down the Internet as he does to fix Mr. Trump’s hair.

Yet I had a different reaction to Mr. Trump and Mrs. Clinton’s fantasy of a world in which you could just shut down parts of the Internet that you didn’t like: Sure, it’s impossible, but just imagine if we could do it, just for a bit. Wouldn’t it have been kind of a pleasant dream world, in these overheated last few weeks, to have lived free of social media?

Hear me out. If you’ve logged on to Twitter and Facebook in the waning weeks of 2015, you’ve surely noticed that the Internet now seems to be on constant boil. Your social feed has always been loud, shrill, reflexive and ugly, but this year everything has been turned up to 11. The Islamic State’s use of the Internet is perhaps only the most dangerous manifestation of what, this year, became an inescapable fact of online life: The extremists of all stripes are ascendant, and just about everywhere you look, much of the Internet is terrible.