That's why I used to do it! (Though not really necessary here, but in other situations.) I didn't let ignorance run rampant. I’ve had long discussions with many people like the ones OP encountered. I never tried to convince them -no, they’re beyond persuasion. The point is to ensure their claims and advice don’t go unchallenged. I did it hoping that others -guests, silent readers -would engage in a bit more critical thinking and make their own judgments about what’s right and wrong in the discussion.