Usually I don't interact with trolls and I let slide a lot of things on twitter because policing is not something I like to do (nor I believe it's the proper action). But when your opinion is full of hate, racism, and prejudice against the south of Italy, then I've a problem.
and that's because it's a prejudice which was driven since the "unity" of Italy. And now it's somehow normalised to chant "Vesuvio, wash them with fire" during a football match
Before the unity of italy, we were (very) rich, had the first railway, second naval force for commerce in Europe, first military academy, and so on and so on. After the unity we suddenly become lazy, dirty, unwilling to work and so on....