Why do some southerners have a problem with northerners ( England)?

I have noticed when I do go down south some of the people have an awful attuned - especially once they find out you're northern, hear the accent they seem to go into defencive I don't want to talk to you mode. I thought we were all one country? we can't all speak the queens English ... accents are a part of who we are . I am sorry if it offends people but there is not a lot I can do about it. So why are some so prejudiced?