I am inclined to say that I agree completely, especially with your idea that "people say nonsensical things about stuff they have no idea about." Confident speculation is completely typical, and might not be a big deal were it not for peoples' inclination to trust authority figures. I have gotten into the habit of fact-checking all the time, simply because it is a good way to learn.
We know lil is a fan of science. Though I bristle at the apparently absolute claim that "Everything we hear is ... not a fact," we are not privileged to handle true and false facts, we deal only with evidence and beliefs. We do so in our flawed ways, and all make mistakes. So maybe it's fair to say that most everything we hear from others is an expression of belief, and not cold, hard facts.
I try to remind myself of this by using language like "in my view" and "it seems" whenever I make factual statements, and also citing my evidence and making clear, verifiable claims, as in the "What are your predictions?" discussion. It's easy for mk to say the legislature is full of "spineless pond scum" but it is not so easy to test this claim.
Thanks for expanding on your thoughts!