Someone has respectfully asked you to not call them a name that they do not like to be called. Your argument is that it is a show of love. IMO, it is a greater show of love to accept that your child does not like the pet name you have for him and you do your best to stop using it. If your son feels so strongly about this he has brought this up with another adult to ask you to stop... you stop. And you acknowledge it shouldn't have gotten to that point: your DS's dad was right to bring it up in front of him, as it lets your son know that his dad will step up to people calling him names. Even names that are considered nice by the name-caller.

FWIW, Liebling doesn't like me calling him Liebling IRL. So guess what: I don't. It's sad. And some day he won't want me calling him My Precious (probs when he reads Lord of the Rings). That's OK too. Doesn't mean he won't always be my precious Liebling. Just that he doesn't like me using that as his name.

And eeek - I'm fine with always being my parents' child, but being their baby would creep me out and it is just wrong. IMO, of course.