I'm richer than most of Shanghainese, I'm well educated than most people in your city. Should I look down upon most of Shanghainese?
When I was in my home province, I heard some people called people outside the province "Bei Lao","Lao Tou","lao song"
I can understand why some Shanghainese have the similar thoughts. Also, I understand why some people, actually many of them from Hongkong call mainland Chinese "ah can".
Personally I feel annoying about those insulting words. Fortunately, those words most likely come out of poor the educated people.