I'm upset at my uncle for petting my cat wrong
How did your uncle pet your cat wrong?
They were picking him up by the tail and petting him upside down.
It makes sense that you want your uncle to treat your cat in a respectful way. Maybe showing your uncle the correct way to pet it would be helpful.
Why are you so calm, I want to punch him.
I suggest showing your uncle how to properly approach and pet your cat next time. They might be unfamiliar with how cats are to be treated. If you show patience, they'll understand your concern.