The reason I say it doesn't exist is because like any nation that is predominantly Nordic/Jewish/WASP, the South of the USA is filled with many. Many are racist and mean. A lot are actually openly arrogant to even each other if they feel they're beneith them.
It's a fact that certain groups -- Italians, non-Visigothic Spanish, Greeks, Germans, Japanese, Chinese, tend to be nicer people than Nords on average. So I don't believe Southern hospitality exists.
Southern hospitality is based off respect from my experience. Race, age, or class has nothing to do with it. I'm Hispanic and live in the south and I do feel the racism daily, but once I prove to people that I'm worthy and deserving of their respect then I am treated like everyone else and that racism goes away quickly. My age doesn't really effect how people look at me. I'm also not the wealthiest person, but I'm still treated fairly despite me not being as wealthy as the people around me. So yes, southern hospitality does it exist, but it isn't given, it is earned.