There are many variants. "Don't be vulgar", but also "don't criticize" or "invent something positive to say, only then can you criticize". "Be lavish in your (insencere) praise".

All this leads to a (despicable to me) culture of always-smiling emotional liars. If something I did is shit, say "it is shit". Make an unhappy face. Don't smile, praise my performance when cooking coffee and on the side mention that my last project "made some people somewhat happy".

But I'm not sure if that answered your question, I didn't fully understand it.