I'll just send you a message so you can elaborate -
[Before I start, a short explanation to all my readers about the reason why I'm writing this post: after reading this post (which I find very interesting), I wrote a note to the OP about that bit concerning North-South discrimination in Italy, because I felt it was very inaccurate. Basically, my message read "cool post but North-South discrimination in Italy isn't race-based but rather socio-economy based". Since the OP has asked me to elaborate on the topic, here we go.]
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Well, basically, the North vs. South Italy conflict has little to no relation with race, since we Italians (that is, except for those who have non-European origins) all feel that we are part of a common European and Christian heritage that I guess could be defined as 'white' by US parameters*, and it's more of a socio-economic nature. North and South Italy don't have much of a common history, since they basically have been politically separated since... well, the fall of the Roman Empire. Therefore, as you can imagine, at the moment of their unification, in 1861, there was a huuuuge difference between them. The North was richer and more industrialized, whereas the South, due to the horrendous Spanish administration, was still basically living in a feudal system. Fast forward to the 'economic boom' of the Fifties: Italy goes from being a mainly agriculture-based economy to being the seventh industrial power worldwide. This change requires an exorbitant number of workforce, and since all the italian industries were based in North Italy, a phenomenon of South-to-North mass emigration began, because, although Italy tried to invest money into trying to convince the industries to build factories in the South too, the project didn't work, and the South remained drastically underdeveloped, while the North was racing forward. Now, remember how I said that North and South Italy haven't really been unified since the days of the Roman Empire? Yeah, just try to imagine how different we can be in terms of culture, habits, behaviour, hell, even frickin' LANGUAGE: the emigration of the Southern Italians to the North was a cultural, social and economical clash of gargantuan proportions. Obviously South Italians weren't seen well because they were considered 'thieves of workplaces', and were, of course, surrounded by prejudices depicting them as ignorant and lazy. Sadly, there are still people who are playing the 'they-are-stealing-from-us' card (the infamous political party Lega Nord, for example, who still obtusely believes in that ridiculous 'the North is better than the South' thing), and slurs such as 'terrone' are still used against people from the South, but generally speaking, things are much better than back then, especially among the younger generations (at least, from what I've seen). Prejudices are hard to kill, but thankfully this toxic mentality is fading away, I believe.
To wrap it up, I'd say that:
1) yes, Northern Italians discriminating on Southern Italians exists, but the phenomenon is not as widespread as you'd think it is, and it's mostly about prejudices rather than actual harmful behaviors, generally speaking. There are exceptions (like the Lega Nord), but I wouldn't say it's as dramatic as the other examples you brought up in your post.
2) no, the discrimination is not race-based as you suggested in your post, but it rather finds its roots in historical, political, social and economical reasons.
3) and last but not least, no, we don't discriminate on Sicilians because of their Moorish/Arabic heritage. Jesus, even writing that sentence down seemed just totally weird to me. The Arab rule over Sicily ended at the beginning of the 11th century, and although many Arabs decided to stay under the Norman rule, basing any type of racial discrimination over the fact that South Italy was ruled by muslims over one thousand years ago seems just... ridiculous. I mean, using the same reasoning you could say that Sicilians are more 'racially pure' because they have Norman heritage too! It just doesn't make sense. (Also, what's about Sicilians that makes them deserve a 'special kind of discrimination'? I mean this ironically, of course, but I'm genuinely interested in the reason why you cited Sicilians in particular).
*I dislike using the term 'white' in non-US contexts because I feel it covers only a little part of our perception of ourselves, which is constructed not only of skin colour, but also of heritage, nationality, language proficiency, ethnic, cultural, social, and even religious background and even more.
