For censoring speech, we have before us two options:

Option A is to ban "mistruths", and to go down the philosophical pursuit of determining what is "fact" and what is fiction, which will change based on milieu, sentiment, those in power, etc., and will be argued endlessly. Then we need to get into "unintended mistruths" vs "intentional mistruths", etc.

Option B is to allow most speech and to only focus on tortious fictions (libel/slander).

I think most sane people would choose Option B. And yes, Iran will disagree with the "facts" of the American populace, as I assume a German will disagree as well :)