The problem was not the event itself, but how it was handled. When people see ships in space run by supposed fellow Capsuleers, they expect they can be killed. I'm glad they were not able to be killed, but not everyone was, and while some were content to bitch about their failed ganks, others brought up the concern that, if event actors are utterly invincible, what point is there in interacting with them.
Ofc it goes to say that there are more ways to 'interact' than trying their best to kill them, but not everyone want that. Not everyone RP, and even among those who do there are those who want to kill the actors, depending on who the players are and actors represent.
In short it seems to boil down to "if it flies in space we should be able to kill it", even if the thing flying in space is rather important for the overall EVE-online story, that arguably loads of people don't care about at all, as opposed to shiny and special kill-mails.