True, and perhaps "common sense", but I think questioning common sense now and then isn't a bad idea.
My theory was, when you find yourself in a situation like this, if you remain cordial and repetitively bring the conversation back to the same question over and over, eventually it will be ~impossible for them to not realize what is happening. I now realize I executed poorly on this until the very end, where it may have suddenly become easily distinguishable that I wasn't just arguing and what was actually going on, but by then it was too late.
As always, I will work on improving my behavior, but my sense is that this general problem continues to grow, here and elsewhere. Censorship has an upper bound of effectiveness, something lower average quality communities are grappling with now. I worry that kicking the can down the road might ultimately not be a good idea.
> if it is possible to get someone who believes something not-absolutely-factual to examine the foundation of those beliefs.
That's extremely unlikely to happen, especially on the internet, and you can do a lot of damage in the process—especially if the way you go about it isn't obviously distinguishable from simply arguing the opposite side.