I suggest it is an invasion of privacy for a crew member to address any passenger by their name in front of others. Perhaps the passenger does want their name known to seatmates. (A celebrity, spousal abuse victim, etc.) Would a crew member announce other personal information in the airline's records about the passenger in front of others? No.
There have been cases of people using a cabin crew members full name to harass them in a hotel, and even at home through the phone book.
The same could occur to the passenger, I expect, once a nut learns their name.