The kid WAS named after him and he IS calling him by a NICKNAME based on his REAL NAME. JR is a nickname based off HIS NAME. It would not be within your right as a mother because he was named (was it James Robert or whatever?) and he is referring to him by that name with a nickname which is so incredibly normal. No it is not disrespectful to the other grandfather, it is so unfair to put that much weight on a name to say that not referring to him by it is disrespecting another man’s existence.

Yeah you’re right, if someone called your kid aids it is in your right to tell them not too because AIDS is a disease that kills people, JR is the kid’s middle initials. Yeah that trope you’re referring to does exist, however he isn’t calling him by the wrong name he’s calling him by his name. You have no clue is “disrespect is no big deal to him because he’s used to his father disrespecting him” because we are supposed to take posts at face value and OP did not say the grandfather has a history of disrespecting him, you made that up on your own.