Opposing opinions are not necessarily nonsense. Not that you said that, but many imply it or assume it. It's like their worldview or nonsense. At best, they allow small diversions from their worldview.
I say, we should allow huge diversions from our worldview.
In fact, even if its nonsense, if its influencial we should study it and understand it (that is, we don't have to suffer any random nonsense, but if something is both nonsense and big, the real active citizen should study it at least, even if just to try to grasp why their fellow people fell for it and what consequences it might have).
Of course if they start with "they fell for it because they're bad/stupid/crazy/lazy etc" that's just something to make themselves feel better, and doesn't really explain everything.
First of all, this or that people can be bad/stupid/crazy/lazy: those are characteristics of the individual. Millions of people can't be said to be that, there are other forces at play when masses make decisions or adopt things, not personal pathologies.
E.g. it's surely it's not because all the "stupid/crazy" people are in the fly-over states that Trump was popular there. And vice versa, it would be improbable that most of the smart/sane people are in the coasts. (You could reverse this with how MAGA supporters view Hillary supports, and it would be the same argument).
Perhaps its a cultural thing that made this people vote this way and the others that. Or a historical thing. Or an economic shift that's felt in one area and not in another. People should strive to understand those things then, instead of assuming the others are into "nonsense".
Of course people conveniently call their fellow people good/sane/etc when they agree with them (e.g. a vote goes how they liked) and then explain the opposite result at some later point (e.g. people voting something they don't like) as "people being bad/crazy/duped/etc"). They're not bothered to see the contradiction in calling the same masses both things at different times.