I certainly don't find the term offensive, I find it amusing and assume it is used with affection (or even affectionate exasperation, on occasions!) Certainly when used by someone like Flapsforty it would clearly be affectionate, as the fact that she has the utmost respect for/empathy with her passengers shines through any of her posts in which she describes her working day.
"Trolly Dolly" is potentially, in my view, far more offensive, because it demeans someone's chosen occupation (in the same way as "quack", "desk jockey" etc).