Heliport
As I said, I wasn't there at the time. I certainly don't have enough facts to make a judgement.
I can see a number of difficulties for anyone wanting to bring a case against the pilots, not least your point that the event was closed to the public at the time.
Another good defence would be that they were honing their skills with the permission of the ATZ controlling authority (I don't think it was ATC at that time?) and not putting on a display for the public.
My concern was more at the personally abusive nature of some of the posts. The public abuse of an identifiable individual by someone who hides his or her own identity is not pleasant.
Mike