What is a stereotype associated with dialects?

A common stereotype among dialects is that British people seem kind of high and mighty. Like they are better than everyone else.

Explanation:

I had a friend who went to school in England and they said that when they would use an English accent, people would tend to be nicer to them. When they would drop the accent, the Brits would talk to him like they were trying to teach algebra to an infant. Personally, I think that they get the impression that all Americans are fat, ugly, stupid, gun loving, idiots and they treat us as such.  

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