Honestly, I think it's just a P.C.-ism. "Immigrant" is out, and "diaspora" is in because it vaguely smacks of victimhood. Middle Easterners may be leaving behind economic hardship, but things were hardly much worse during the Irish potato famine.
Which is why folks have written about the Irish diaspora. I didn't say I agreed with it, I said I could understand it in the context. I think it smacks of PC to try to regulate how people use words in general. The original Diaspora to the Persian empire was less a matter of forced removal of Jews from Jerusalem and its environs than the later Roman-induced diaspora as a consequence of the their losing a war of rebellion. That diaspora more to do with Cyrus allowing subjects from different parts of his empire to immigrate to Babylon.
I myself would probably not use the term anyway. As it evokes all kinds of problematic rhetoric.
