Seriously though, could it be a company instruction that crew should try to get people to stop filming (for any number of reasons) and that crew fear that if they do not then they will be disciplined or at least called up on it?
If it is a company policy, and is a legal restriction of the freedom of pax, then it must be notified in the passenger announcements which already include such things as use of mobile phones & electronic devises etc. On all the various airlines I've flown on I've never heard such an announcement.
I would have thought that video evidence would be very helpful in bringing a prosecution after the event. Taking 188 pax statements + 4 C/A's would be very time consuming and could well lead to a confusing picture of the true events.