I am not in a position to comment on the question of the OP.
What Sabine refers to in UK is still quite common though, and almost invariably innocent, and rather regional too. In different parts of the country, and always more commonly in the north than the south, people may be called love, or my love, pet, hen, duck, flower (in the south-west), chuck, sweetheart etc and it is very rarely seen as offensive, although I cannot imagine trying to teach a non-native speaker how or when to use them!
One of the large supermarkets banned the use of "love" by staff to customers a few years ago, I think in the north east, but I remember the ban was lifted fairly rapidly.
On the contrary, I find being called 'sir' usually not very complimentary. Police men and women do it, though I have had very little to do with them. A security guard in Stansted airport used it 'at' me on Monday in a way which I found rude and condescending, which is strange, as it seems like it should be a term of respect. He was being rude in a fairly indiscriminating way to everybody, which I found embarrassing on behalf of the many foreign visitors. It can be respectful, but is not universally so.