Perpetuating mistakes doesn't mean they're not mistakes. Calling it a custom doesn't mean it's not a mistake. If you want to be contrary, fine, but don't expect people to stop correcting your mistakes either.
No, it really is just a different custom, a different form of address used by most of the population. Despite what you say, it's not a mistake to them
to address ships like that.
It really isn't anything to get very upset about.