[wwweston]

This borders on epistemological nihilism. Of course few assertions about truth should be beyond challenge. Of course there are grades of confidence and properly conducted discourse (including venues/methods of challenge) can improve the quality of conclusions. That doesn't mean there's no such thing as poor-grade or even garbage assertions.

And functional institutions not only have a responsibility to try and establish some kind of reasonable consensus about the truth, they basically can't operate without doing so.

When courts make rulings, they can't do it without establishing facts of a case. That's not "presuming" so much as it is simply functioning. There's a process for arguing details out... and an end at which details are accepted as established. Potentially subject to review, but not arbitrarily.

[mountainboy]

"The sky is blue". Ok, we pretty well agree on that. But do I perceive "blue" in the same way that you do? We'll never know.

Regardless, people are not using the term "misinformation" in that way. They are using it for phenomena we cannot all readily observe for ourselves, and for which there is a claimed, but not actual consensus.

800 years ago it was "misinformation" to claim that the Earth orbited the Sun. Today it is "misinformation" to claim that germ theory is incorrect or that vaccines are not always "safe".

But the people using and spreading the "misinformation" meme are human and have imperfect knowledge just like everyone else. Indeed, they seem closed-minded and intolerant of others' opinions. For me, if a person uses that term, it is a clear signal that the person is wedded to a particular worldview and it is pointless to even engage them in conversation on the topic in question.