Why are southern Americans stereotyped as uneducated and ignorant?

Also generalized as racist and severely homophobic. I had a conversation with one of my mother’s coworkers who came to dinner at the house who was originally from the southern United States and she opened up about her struggles up here in the northern U.S. people seemed to think she was uneducated and ignorant based on her strong southern accent. And seemed surprised she has a higher education ( she has up to a masters degree). She is not racist or homophobic. And yes she is deeply spiritual/ religious but a moderate in social and political views. I felt sorry for her honestly. Being from the south doesn’t mean you are a gay bashing kkk loving xenophobic dumb hillbilly. And even then there are some people who are considered hillbillies but are actually quite smart and broad minded. She is from Texas originally and lived in Georgia before she moved north. There are elite universities and strong economic opportunities in different parts of the southern United States. There are even liberals in the south. So just thought I would mention it.