That's not true at all.

In Italy centuries ago most people stayed in small villages or did not leave them for a larger city or a new country, before Italians emigrated to the United States and other countries.

Back then people had what we would consider large families and families from a village, or nearby village would marry each other, or sometimes have arranged marriages.

I have friends who are Southern Italian and they told me how when they went to Northern Italy when they spoke with a Southern accent, that people in the North who were from there became nervous.

But they did not say it was actual hate that they received from Northern Italians; but they did tell me about the slur Northern Italians have and use for Southern Italians or the word 'terrone' which they said basically means the person is akin to an uneducated redneck; but it does not really translate that well into English since it's an Italian word.

However I have a friend that is part Southern Italian, and she said when she, and her family including her Italian father who was from Naples went to central or Northern Italy when he was alive it was no big deal at all that she and her father were Southern Italian. Nobody thought her father did not speak Italian correctly.