Both of those definitely changed; unlike some of the other things you say, this is not ridiculous. However, I can easily imagine finding in, say, the personal correspondence of Archimedes, a statement like "this idiot tried to show me another squaring-the-circle proof again". We do preserve personal correspondence in ancient records, and that sort of thing doesn't require a lot of access.
> No harm in being wrong on the internet.
http://www.mamapedia.com/article/mmr-vaccination
Money quote: "I have really close friends who swear that within 24 hours of the MMR their child had symptoms of autism"
> Politeness is more important than rightness as a rule to enforce.
It's better to be right. Enforcement of politeness greatly retards, and can prevent, the discovery / acknowledgement of rightness.
> Rightness sorts itself out among able and interested parties.
This can be tautologically true, depending on your definition of "able". It's very clear that rightness does not sort itself out among interested parties, and they can be harmed thereby.
To me it seems you're contradicting yourself. What does this bold statement of yours tells you about trying to contribute to a problem one does not understand?
"The essay reflected that ______" reports someone else's point of view, not my own. I agree that something is wrong in our culture; it cannot be shown that this represents a change from that of Classical Greece, but it can be supposed to varying levels of certainty. But if I exhort people to stop contributing to a problem of today, whether that problem originated in the recent past or the ancient past is of no relevance. We should still stop it today.