The mental model of how you use a certain branch could indeed be best expressed by the word "main", so no one can say the word isn't the best one for you to use.
But a master copy or version of something like a master recording or gold master for pressing records is different from merely "main".
Applied to software they are similar but not identical concepts, and neither is in any way wrong or harmful to anyone.
It's a small enough issue that it's not worth fighting very hard over, but, the rationale for the change, and especially for anyone trying to tell anyone else they have to do that change, is still invalid and the word master actually applies better if that's how you're using that branch. It has nothing to do with slave bosses.
But a master copy or version of something like a master recording or gold master for pressing records is different from merely "main".
Applied to software they are similar but not identical concepts, and neither is in any way wrong or harmful to anyone.
It's a small enough issue that it's not worth fighting very hard over, but, the rationale for the change, and especially for anyone trying to tell anyone else they have to do that change, is still invalid and the word master actually applies better if that's how you're using that branch. It has nothing to do with slave bosses.