Generally the matter is one of blood purity, as with all racism. Southern Spain, Italy, and Greece were all occupied at one time by Arabs, which contributed certain hair textures, skin tones, and facial features to the local gene pool. Those with no knowledge of history or civilization tend to be terrified of acknowledging the artistic and cultural contributions of al-Andalus and the Ottoman Empire. As you probably know, the northern reaches of Italy are more German than Romance, on account of those pesky invasive Lombards.

Of course the true absurdity of all this comes when two people from the same parents end up with different physiognomical and racial labels; since these traits are rarely as simple as idealized Mendelian characteristics, it is entirely possible for them to be passed on a couple of generations before re-coalescing. (The case of Summer on The Sopranos comes to mind—while her parents both have fairer skin than she does, the result is otherwise not all that unrealistic.)