Unfortunately, that kind of conspiracy theory isn't just reserved for isolated nutjobs. Trying to remain neutral about it, it is either the case that tens of millions of Americans believe in a conspiracy of scientists to promulgate a hoax about the climate, or tens of millions of Americans believe in a conspiracy of business interests to hide the reality of climate change.

That's not an ordinary difference of political opinion. One side or the other is engaging in conspiracy-theory thinking, at a vast level. (Or, I suppose, both.) I don't just mean that they're talking about a conspiracy, but applying all the hallmarks of paranoia, shifting goalposts, and bad faith that mark conspiracy theorists.

And that's just one example. It applies down the line, of many issues. This is the one that perhaps illustrates it best, but it's not mere partisanship. It's people needing to be "brought back to earth", as you said, but at a level involving many millions of people.