This is ridiculous. Italians do not hate sicilians and vice versa. I've been in Sicily plenty times in August when mainlanders come down to vacation in Sicily. There is no animosity.

What I have seen, is Sicilians coming over to the US, and sticking with their own kind. And by their own kind, I mean other immigrants, not sicilian-americans.
They don't trust anyone as a rule, though. Not even each other.