R.K.
My youngest son is 21 and 6' 2", 30" waist, I call him 'Little Boy" all the time. He just laughs. But if he said hey Mom knock it off I would.
When my oldest daughter, Jenni, was 5 or 6 she told me she did not want to be called by her baby nickname any more, which was Nifer (short for Jennifer) she wanted to be called Jennifer. I respected her wishes, her paternal grandma called her Nifer and I said " she asked not to be called that anymore she wants to be called Jennifer" grandma's reply "I can call her whatever I want". But that woman called all of her kids by their baby nicknames until she died.
To teach a child respect --- they need to be shown respect.