How did you arrive at the conclusion that the "average user here is neither an expert in practically anything, nor likely a productive member of society"? I disagree with many users, but have no reason to indict them.
That's exactly why you are wrong. In your world, upvotes are based on niceties and political correctness, but in my world that should be based on experience and expertise.
And:
If you believe that anger and defensiveness harm rational thinking.
And:
That being rude is liable to make people angry and defensive.
Then - regardless of what world you'd rather live in - being condescending and arrogant seems liable to be ill aligned with your aims.
Neither niceties/political correctness or experience/expertise should be reasons for an upvote unless the answer is correct or insightful.