In which a historical objection is raised:
I’ve read that the two migrations of Greeks into Italy (the first around Cato the Younger’s time IIRC, and the second after the fall of Constantinople) were beneficial for Italian society because of the Greek learning and culture they brought with them. Are these relevant to your thesis about the negative effect of immigration on receiving societies? As an immigrant to Italy, what is your opinion?
Cato the Younger lived from 95 to 46 BC. Julius Caesar crossed the Rubicon in 49 BC. The Roman Republic is considered to have ended in 29 BC. I submit that this specific example is very relevant to my thesis, insofar as decades of civil war followed by a collapse into one-man dictatorship would generally be considered to be a societal negative.
As for the second wave of Greek immigration, those were Greeks in the Byzantine sense, not the Hellenic. Since Byzantium was still somewhat more civilized than thrice-sacked Rome or the oft-invaded Italian peninsula, this is rather like asking if immigration from the United States to some of the more war-torn African societies would be beneficial. And remember, the difference between Byzantium and the Italian peninsula would likely have been even starker were it not for the Venetian conquest and sack of Constantinople in 1204.