So if someone pronounces your name wrong, you don't correct them, because it would be impolite? If the clerk at a store gives you incorrect change, you don't bring it to their attention? Someone may not have known they've made an error unless someone tells them. And I didn't tell anyone off. I politely informed said family member that as an adult, I should be getting my own invitation, for future reference. This family member didn't even start adding my name to invitations until my mother asked her enough times about various events whether I was invited too when it was obvious I was, because we're talking things like a kids birthday party in the backyard, not a wedding or somesuch.
hey, its your life, do with it what you will. if that makes you happy and makes you feel better, go for it. just saying, pointing out etiquette matters like this is actually against etiquette. so you have to decide if two wrongs make a right.
bit difference between pointing out a mispronounced name (my lot in life, btw) and such. I'd tell someone if they had spinach in their teeth, too. but there are polite ways of doing so, and its not about teaching someone a lesson