I've always hated this disingenuous line of arguing. Yes, technically there were some black people in Italy, but these types of arguments always frame it in such a way that it seems like it was a common thing to witness for the average citizen. The large, large majority of Italians (we're talking in the past obviously) have never seen anything other than other Italians, and those few foreign black people were very much a rarity.
Hell, go to places like Serbia today as a black man and you'll be gawked at like you're an alien, even in the capital Belgrade, yet alone in the smaller cities. Or do the flipside, go to a remote part of a country like Indonesia as a white man, like a random village in Papua or even a city like Jogja (and it's not exactly a small or unpopular city either), and you'll similarly be gawked at.
I'm a Serb (so corpse-white when I don't tan) but lived in Indonesia my whole life, I can't tell you the number of times I've been in situations where people have looked at me in fascination because of my white skin, even in places where tourists are common. If you go to Borobudur as a white person, you're going to be asked to have your picture taken by a dozen curious Indonesians who have never in their lives seen a white person in real life, and this is a massively popular tourist spot in a pretty massive city with plenty of foreigners coming and going.
So sure, there were some black people in Italy, but let's not pretend like that was anywhere near the norm or something you could expect to see every day in 1700s Italy as an average Italian.