Yes indeed in the sense that if someone uses the name “Fatso” everybody including Fatso himself knows exactly who is being referred to. It’s illogical to deny that your name is by definition what other people call you. You don’t go around saying “severus68 posts on CAF”, you say “I post on CAF”.
It’s clear you just want to be right. Logic and social graces have nothing to do with your argument.
The name of the young child, for example, being bullied by his classmates would NOT be “Fatso”. Even if everyone knows who they are talking about.
Just like the name of the bullying children would not be “bully”. Although, it quite applies doesn’t it?
Now, if the child whom all call Fatso, says “hey, just call me ‘Fatso’”, Then yes, it’s ok to use that as a NICKname. Everyone has been given permission from the body that will respond to the call. But you can bet, unless he makes a legal name change, when he grows up, he won’t be signing his mortgage as Fatso Petergee.
If, however, that child does not want to be called “Fatso”, then it is no one’s right to decide otherwise. Will they still likely do it? Yes, because they are bullies. They feel it’s their right to do as they wish and treat people however they like. But they would be wrong. And you know this.
I suppose you are more than welcome to call people as you wish. Just as they are more than welcome to acknowledge your existance or not when you try to make an example of them and enforce your opinions of their life.

I know I answer to my name. I also do not answer to any version people like to apply to me, especially when they’ve been asked not to, or corrected. We all have choices to make.
To further my explanation. My legal name is First Name, Maiden Name-Married Name.
I don’t have a problem going by either last name. Except in the Business world, where my internationally functioning business is tied to my maiden name. Ahhhh-haaa. DH likes the money I bring in while sitting at home. So he has no issue with people that work with me, thinking of me or addressing me as: First Name Maiden Name.
Also, our children go by married name. I don’t need any nut jobs tracking them down by knowing a few too many pieces of my information. I’m sure the safety of my children is a stupid reason in your book to do what I have done with my name. Most people at their school call me Mrs. Married Name. I don’t have a problem with this. My Maiden Name - Married Name is a mouthfull. Generally speaking I’m relaxed enough I offer adults the option to Oh MY! Wait for it! Please, call me by my FIRST Name.
My problem with YOUR statements is that you make it quite clear, that a woman could be introduced as Mrs. Maiden name - Married name, and because she has “stupidly” done such a thing with her name, seemingly with her own husband’s approval, you feel it’s only right to correct her “stupid, non committed idea” and call her Mrs. Married Name. You do it to teach a lesson so to speak. To show just how smart you are, and how stupid they are. And in your simplified words to correct the error of their ways. You become the bully. You make it clear this is your entent. As everyone in your neck of the woods rolls their eyes at the women that do this. As if it weren’t done with discussion and agreement with their spouse. Who, if Catholic, committed themselves to a marriage, valid unless proved otherwise, under the guidance of an approving priest. Please show your credentials at this point. Your OPINION is just that.
I wonder, have you ever given thought that perhaps the hyphenated name belongs entirely to her husband, and you just butchered it? That would easily happen where I live.