I think CC have been joking about eye-drops in pilots dinner for most of them. Thats not to say that it is acceptable, or even that it is ever done; what can be said as a joke in the galley though does not translate well in black and white. Most of the 'guilty' crew in this category never intended this as a threat, or even that it would be construed as such. If anything it was a poorly timed joke and, if english is not their first language then they may not have realised how it could be misconstrued. Am I the only one who thinks this?
Joke or not, there was a previous high profile case of crew threatening to poison a pilot a few years back, I believe it was the origin of the term 'Dranse Day/Tours'.
I think this also ended with a police investigation, it was well documented on the old Bassa Forum at the time so I surprised to see it happen again, some crew never learn.