It's not just about upsetting the other person, it's more about the end goal. If the end goal is to express superior knowledge, do strike down your hammer of truth.

But if the end goal is to enlighten the people around you, and let them enlighten you, then it matters how you package your truth. Sadly it's seems to be human nature that if you tell someone that their perspective of the universe is wrong and don't give them any leeway, there's a high chance of them just dismissing it because it would hurt them.

Now if you are more diplomatic with your self devised absolute thruths, you might find that the people on the receiving end are more willing to accept them.

This concept seems to be fully absent from politics these days.