I'm not that familiar with defamation laws in Europe and really don't think there's any real realistic exposure for most of them. Peter Quennell is probably the most vulnerable in the U.S. I think because he clearly just makes things up. But even then, probably not that vulnerable. But hey, if they want to scrub their sites, have at it.
Just responding here, and I don't know if anyone else has gotten to this.
But the laws against defamation/calunnia, are much stronger in ITALY THAN IN THE US.
There are laws in the US at the federal level that specifically protect US citizens rights to speech, that may well violate laws of another country. For instance, in Thailand, its a crime to insult the king.
Different states provide another layer of protection. IIUC, NY state actually has the strongest protection (Go NY!).
However, that in no way is protection against the US laws of course. In the US, IIUC its just a higher burden of proof.
SO, the issues are not as draconian as people may think.
However, these people must know on some level that what they do is outrageous, and that after the ISC verdict, they need to be more careful. What's lovely about paranoids who see plots behind every corner, is that they can be expected to over-correct.
Anyway, I doubt they'd get sued for anything written in the past. But anything written after the verdict, I think crosses a bright line, and they're caution is prudent.
Of course, they're idiots to begin with.