Objectively, I don;t think 'hate' is an appropriate adjective, but I do think there are difinite differences which need to be understood.
One of the reasons why northerners can dislike southerners is the unspoken perception that London is the most important place in the world.
Witness the recent snow in the south - suddenly because all the media Tristrams can't get to work, it's a massive news story!
I as a freelance music writer often request albums from record labels, and they usually say "We'll bike it over for you ..." the unspoken assumption is that as a 'media person', I must live within the M25 - in fact I am 160 miles from London.
A large proportion of nothern people are parochial, and view with suspicion people who appear more sophisticated and apparently egotistical, and this tends to further the perceived 'differences' between them.
As a Midlander born and bred, I would never contemplate living in the south, but I work there often, and liase with people perfectly happily, as i do with people all over the UK and abroad, but it is easy to see why the 'differences' are handed down even today.