This is a ridiculous assertion. That might be true if mainstream culture was polite. But it isn't.

It's unfailingly polite regardless of how cruel it is.

Give me an example of a counterculture that was not derided as rude by the mainstream of the time?

That is ridiculous. Newscasters are far less polite and far more openly partisan, combative, and opinionated than they use to be. Comments on articles and videos, and in social media, are far less polite than people replying with letters to the press in the past.

I guess you should be considered lucky for not being exposed to the Freeper comments section 20 years ago, or Fox News comments sections, or Patch.com comments sections. They've always been bad.

Elon musk argued that calling someone a pedophile was within bounds of polite banter on Twitter and people agreed with him.

I'm pretty sure if you ask anyone they would say there was nothing polite about that exchange. By what definition was that exchange polite? None that are based in reality or relevant.

I'm not interested in arguing about the definitions of words.

I think you are saying that mainstream culture has adopted rude behavior, while I am saying that any behavior adopted by mainstream culture is, by definition, not rude.