Paris is 80% people from the rest of the country. Which their former neighbours promply hate as soon as they move there.
It’s traditional.
From what my former Parisian grad school housemate told me, I concur. He once said in reply to a friend (named Roger) asking him why people in Paris were mean to him and hate Americans, my housemate replied, “Oh Rogers, zhee French do not hate Americans, zhey hate EVERYONE, especially zhee other French”. My experience in Paris was that the Parisians were surprisingly friendly. But I speak a little French and say Bonjour and Merci when warranted.