Humans in general have always struggled with precision(insert picture of Trump here). Time shows us an undulating arc of progress regarding most precise thought. As you pointed out precision is degraded in various amounts directly related to the level of intellectual laziness that occurs in the conveyance of a thought. In my opinion life is a relay. Therefore we should all be soldiers in the war against ignorance by passing on what we know well. The people closest to us are the most deserving of our best effort to inform them in what we know well. We also owe them our best effort to understand, trust, and absorb what they know well. With that said, you can't pick your family so it's not always going to be an even trade. When I'm confronted with bombastic ignorance I just start asking them questions about where they got their information. That usually works.

I intervene only if it's so bad, or has terrible potential outcome. Other times I mostly get the " well, not everything you learned at school is right" and" but my anecdotes!". Often times it ends with a variation of dismissive shit like "well I lived my whole life without this and I turned out fine/make more money/am better". So if it's not worth it, I leave it change the subject to butts