Here's a thought: why don't YOU shut up? /s

Sorry! That was mean, but I hope it came across as funny.

In all seriousness, I like the question, and your implication is intuitive: if we (as individuals) talk to machines rudely, it's likely to (at minimum) lead us to be ruder to other humans, if only by habit. And if they're expecting more politeness than we're showing, they may infer the intent to be rude, and react accordingly. Those who are rude would end up being worse off.

That said, it's the Fallacy of Composition to assume that if everyone gets ruder the collective effect would be the same as the individual effect. We have different requirements for what counts as "polite" in different cultures but everyone seems to get along pretty well. Maybe societies can all get ruder (and just get along worse with each other) but also maybe they can't.

I tried looking in the literature but this book implies we don't even know how to measure politeness differences between languages: https://books.google.com/books?hl=en&lr=&id=MPeieAeP1DQC&oi=...

There are even theories that politesse can lead to aggression: https://www.jstor.org/stable/2695863

Deborah Tannen (the linguist) has found many examples where different politeness expectations (particularly across the cultural divide that aligns with gender) can lead to conflict, but it always seems to involve misunderstandings due to expectations: https://books.google.com/books?hl=en&lr=&id=YJ-wDp7CJYAC&oi=...

So yeah, bad outcomes feel intuitive but I don't think linguistics or sociology has a theory of what happens if a group collectively gets less polite.